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9599_14	of Bill C-333 with Bill C-331, a bill to recognize past wrongs against Ukrainian Canadians during wartime, causing Bill C-333 to die when Prime Minister Martin's Liberals lost a motion of non-confidence and parliament was dissolved on November 28, 2005.
9599_15	Political campaigning
9599_16	As they had done while campaigning for the federal election in 2004, the New Democratic Party and Bloc Québécois stated, during the leadup to the January 2006 election, their support for an apology and redress for the head tax. Similarly, on December 8, 2005, Conservative Party leader Stephen Harper released a press statement expressing his support for an apology for the head tax. As a part of his party platform, Harper promised to work with the Chinese community on redress, should the Conservatives be called to form the next government. Before his party ultimately lost the election, Martin issued a personal apology on a Chinese language radio program. However, he was quickly criticized by the Chinese Canadian community for not issuing the apology in the House of Commons and for then trying to dismiss it completely in the English-speaking media on the very same day. Several Liberal candidates with significant Chinese-Canadian populations in their ridings, including Vancouver-Kingsway
9599_17	MP David Emerson and the Minister of State for Multiculturalism and Richmond MP Raymond Chan, also made futile attempts to change their positions in the midst of the campaign. Others, such as Edmonton Centre MP Anne McLellan lost her riding to Conservative MP Laurie Hawn.
9599_18	Apology The 2006 federal election was won by the Conservative Party, forming a minority government. Three days after the ballots had been counted on January 23, but before he had been appointed prime minister, Harper reiterated his position on the head tax issue in a news conference: "Chinese Canadians are making an extraordinary impact on the building of our country. They've also made a significant histo rical contribution despite many obstacles. That's why, as I said during the election campaign, the Chinese Canadian community deserves an apology for the head tax and appropriate acknowledgement and redress."
9599_19	Formal discussions on the form of apology and redress began on March 24, 2006, with a preliminary meeting between Chinese Canadians representing various groups (including some head tax payers), heritage minister Bev Oda, and Parliamentary Secretary to the Prime Minister resulting in the "distinct possibility" of an apology being issued before July 1, 2006, to commemorate the anniversary of the enacting of the Chinese Exclusion Act of 1923. The meeting was followed by the government's acknowledgement, in the Speech from the Throne delivered by Governor General Michaëlle Jean on April 4, 2006, that an apology would be given along with proper redress.
9599_20	That year, from April 21 to 30, the Crown-in-Council hosted public consultations across Canada, in cities most actively involved in the campaign: Halifax, Vancouver, Toronto, Edmonton, Montreal, and Winnipeg. They included the personal testimony of elders and representatives from a number of groups, among them the Halifax Redress Committee; the British Columbia Coalition of Head Tax Payers, Spouses and Descendants; ACCESS; the Ontario Coalition of Head Tax Payers and Families; the CCNC; and the Edmonton Redress Committee of the Chinese Canadian Historical Association of Alberta and Chinese Canadian Redress Alliance.
9599_21	Some considered that the major issues revolve around the content of any settlement, with the leading groups demanding meaningful redress, not only for the handful of surviving "head tax" payers and widows/spouses, but first-generation sons/daughters who were direct victims, as told in the documentary Lost Years: A People's Struggle for Justice. Some have proposed that the redress be based on the number of "Head Tax" Certificates (or estates) brought forward by surviving sons and daughters who are still able to register their claims, with proposals for indivi dual redress, ranging from $10,000 to $30,000 for an estimated 4,000 registrants.
9599_22	On June 22, 2006, in the House of Commons for the first session of the 39th Parliament, Prime Minister Stephen Harper delivered an official apology to Chinese Canadians. During his address Harper spoke a few words in Cantonese, "Ga Na Daai Doe Heep" (, 'Canada Apologizes'), breaking the Parliamentary tradition of speaking either English and French in the House of Commons. The apology and compensation was for the head tax once paid by Chinese immigrants. Survivors or their spouses were paid approximately CAD$20,000 in compensation. There were only an estimated 20 Chinese Canadians who paid the tax still alive in 2006. As no mention of redress for the children was made, the Chinese Canadian community continues to fight for a redress from the Canadian government. A national day of protest was held to coincide with Canada Day 2006 in major cities across Canada, and several hundred Chinese Canadians joined in local marches. Documentaries
9599_23	See also Chinese Canadian National Council New Zealand head tax White Australia Policy Anti-Chinese legislation in the United States Chinese Exclusion Act Chinese Immigration Act, 1923 Chinese Immigration Act of 1885 Lost Years: A People's Struggle for Justice Internment of Japanese Canadians References External links Search for names in Canadian government head tax records LOST YEARS: A People's Struggle for Justice - International Award-winning epic documentary, 2011 Transcript of Prime Minister Harper's apology in Parliament National Post-Chinese Cdns Speak of Anger, Anguish - April 23, 2006 Redress.ca HeadTaxRedress.org ChineseHeadTax.ca Anti-Chinese legislation Chinese Canadian Head Tax History of immigration to Canada Human rights abuses in Canada Political history of Canada Taxation in Canada Anti-Chinese sentiment in Canada Poll taxes zh:人頭稅
9600_0	In solid-state physics, the electron mobility characterises how quickly an electron can move through a metal or semiconductor when pulled by an electric field. There is an analogous quantity for holes, called hole mobility. The term carrier mobility refers in general to both electron and hole mobility. Electron and hole mobility are special cases of electrical mobility of charged particles in a fluid under an applied electric field. When an electric field E is applied across a piece of material, the electrons respond by moving with an average velocity called the drift velocity, . Then the electron mobility μ is defined as Electron mobility is almost always specified in units of cm2/(V⋅s). This is different from the SI unit of mobility, m2/(V⋅s). They are related by 1 m2/(V⋅s) = 104 cm2/(V⋅s).
9600_1	Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small number of electrons with high mobility for each, or a large number of electrons with a small mobility for each. For semiconductors, the behavior of transistors and other devices can be very different depending on whether there are many electrons with low mobility or few electrons with high mobility. Therefore mobility is a very important parameter for semiconductor materials. Almost always, higher mobility leads to better device performance, with other things equal. Semiconductor mobility depends on the impurity concentrations (including donor and acceptor concentrations), defect concentration, temperature, and electron and hole concentrations. It also depends on the electric field, particularly at high fields when velocity saturation occurs. It can be determined by the Hall effect, or inferred from transistor behavior. Introduction
9600_2	Drift velocity in an electric field Without any applied electric field, in a solid, electrons and holes move around randomly. Therefore, on average there will be no overall motion of charge carriers in any particular direction over time. However, when an electric field is applied, each electron or hole is accelerated by the electric field. If the electron were in a vacuum, it would be accelerated to ever-increasing velocity (called ballistic transport). However, in a solid, the electron repeatedly scatters off crystal defects, phonons, impurities, etc., so that it loses some energy and changes direction. The final result is that the electron moves with a finite average velocity, called the drift velocity. This net electron motion is usually much slower than the normally occurring random motion. The two charge carriers, electrons and holes, will typically have different drift velocities for the same electric field.
9600_3	Quasi-ballistic transport is possible in solids if the electrons are accelerated across a very small distance (as small as the mean free path), or for a very short time (as short as the mean free time). In these cases, drift velocity and mobility are not meaningful. Definition and units The electron mobility is defined by the equation: where: E is the magnitude of the electric field applied to a material, vd is the magnitude of the electron drift velocity (in other words, the electron drift speed) caused by the electric field, and µe is the electron mobility. The hole mobility is defined by a similar equation: Both electron and hole mobilities are positive by definition. Usually, the electron drift velocity in a material is directly proportional to the electric field, which means that the electron mobility is a constant (independent of the electric field). When this is not true (for example, in very large electric fields), mobility depends on the electric field.
9600_4	The SI unit of velocity is m/s, and the SI unit of electric field is V/m. Therefore the SI unit of mobility is (m/s)/(V/m) = m2/(V⋅s). However, mobility is much more commonly expressed in cm2/(V⋅s) = 10−4 m2/(V⋅s). Mobility is usually a strong function of material impurities and temperature, and is determined empirically. Mobility values are typically presented in table or chart form. Mobility is also different for electrons and holes in a given material. Derivation Starting with Newton's Second Law: where: a is the acceleration between collisions. F is the electric force exerted by the electric field, and is the effective mass of an electron. Since the force on the electron is −eE: This is the acceleration on the electron between collisions. The drift velocity is therefore: where is the mean free time Since we only care about how the drift velocity changes with the electric field, we lump the loose terms together to get where
9600_5	Similarly, for holes we have where Note that both electron mobility and hole mobility are positive. A minus sign is added for electron drift velocity to account for the minus charge. Relation to current density The drift current density resulting from an electric field can be calculated from the drift velocity. Consider a sample with cross-sectional area A, length l and an electron concentration of n. The current carried by each electron must be , so that the total current density due to electrons is given by: Using the expression for gives A similar set of equations applies to the holes, (noting that the charge on a hole is positive). Therefore the current density due to holes is given by where p is the hole concentration and the hole mobility. The total current density is the sum of the electron and hole components: Relation to conductivity We have previously derived the relationship between electron mobility and current density Now Ohm's Law can be written in the form
9600_6	where is defined as the conductivity. Therefore we can write down: which can be factorised to Relation to electron diffusion In a region where n and p vary with distance, a diffusion current is superimposed on that due to conductivity. This diffusion current is governed by Fick's Law: where: F is flux. De is the diffusion coefficient or diffusivity is the concentration gradient of electrons The diffusion coefficient for a charge carrier is related to its mobility by the Einstein relation: where: kB is the Boltzmann's constant T is the absolute temperature e is the electrical charge of an electron
9600_7	Examples Typical electron mobility at room temperature (300 K) in metals like gold, copper and silver is 30–50 cm2/ (V⋅s). Carrier mobility in semiconductors is doping dependent. In silicon (Si) the electron mobility is of the order of 1,000, in germanium around 4,000, and in gallium arsenide up to 10,000 cm2/ (V⋅s). Hole mobilities are generally lower and range from around 100 cm2/ (V⋅s) in gallium arsenide, to 450 in silicon, and 2,000 in germanium. Very high mobility has been found in several ultrapure low-dimensional systems, such as two-dimensional electron gases (2DEG) (35,000,000 cm2/(V⋅s) at low temperature), carbon nanotubes (100,000 cm2/(V⋅s) at room temperature) and freestanding graphene (200,000 cm2/ V⋅s at low temperature). Organic semiconductors (polymer, oligomer) developed thus far have carrier mobilities below 50 cm2/(V⋅s), and typically below 1, with well performing materials measured below 10. Electric field dependence and velocity saturation
9600_8	At low fields, the drift velocity vd is proportional to the electric field E, so mobility μ is constant. This value of μ is called the low-field mobility. As the electric field is increased, however, the carrier velocity increases sublinearly and asymptotically towards a maximum possible value, called the saturation velocity vsat. For example, the value of vsat is on the order of 1×107 cm/s for both electrons and holes in Si. It is on the order of 6×106 cm/s for Ge. This velocity is a characteristic of the material and a strong function of doping or impurity levels and temperature. It is one of the key material and semiconductor device properties that determine a device such as a transistor's ultimate limit of speed of response and frequency.
9600_9	This velocity saturation phenomenon results from a process called optical phonon scattering. At high fields, carriers are accelerated enough to gain sufficient kinetic energy between collisions to emit an optical phonon, and they do so very quickly, before being accelerated once again. The velocity that the electron reaches before emitting a phonon is: where ωphonon(opt.) is the optical-phonon angular frequency and m* the carrier effective mass in the direction of the electric field. The value of Ephonon (opt.) is 0.063 eV for Si and 0.034 eV for GaAs and Ge. The saturation velocity is only one-half of vemit, because the electron starts at zero velocity and accelerates up to vemit in each cycle. (This is a somewhat oversimplified description.)
9600_10	Velocity saturation is not the only possible high-field behavior. Another is the Gunn effect, where a sufficiently high electric field can cause intervalley electron transfer, which reduces drift velocity. This is unusual; increasing the electric field almost always increases the drift velocity, or else leaves it unchanged. The result is negative differential resistance. In the regime of velocity saturation (or other high-field effects), mobility is a strong function of electric field. This means that mobility is a somewhat less useful concept, compared to simply discussing drift velocity directly.
9600_11	Relation between scattering and mobility Recall that by definition, mobility is dependent on the drift velocity. The main factor determining drift velocity (other than effective mass) is scattering time, i.e. how long the carrier is ballistically accelerated by the electric field until it scatters (collides) with something that changes its direction and/or energy. The most important sources of scattering in typical semiconductor materials, discussed below, are ionized impurity scattering and acoustic phonon scattering (also called lattice scattering). In some cases other sources of scattering may be important, such as neutral impurity scattering, optical phonon scattering, surface scattering, and defect scattering.
9600_12	Elastic scattering means that energy is (almost) conserved during the scattering event. Some elastic scattering processes are scattering from acoustic phonons, impurity scattering, piezoelectric scattering, etc. In acoustic phonon scattering, electrons scatter from state k to k', while emitting or absorbing a phonon of wave vector q. This phenomenon is usually modeled by assuming that lattice vibrations cause small shifts in energy bands. The additional potential causing the scattering process is generated by the deviations of bands due to these small transitions from frozen lattice positions.
9600_13	Ionized impurity scattering Semiconductors are doped with donors and/or acceptors, which are typically ionized, and are thus charged. The Coulombic forces will deflect an electron or hole approaching the ionized impurity. This is known as ionized impurity scattering. The amount of deflection depends on the speed of the carrier and its proximity to the ion. The more heavily a material is doped, the higher the probability that a carrier will collide with an ion in a given time, and the smaller the mean free time between collisions, and the smaller the mobility. When determining the strength of these interactions due to the long-range nature of the Coulomb potential, other impurities and free carriers cause the range of interaction with the carriers to reduce significantly compared to bare Coulomb interaction.
9600_14	If these scatterers are near the interface, the complexity of the problem increases due to the existence of crystal defects and disorders. Charge trapping centers that scatter free carriers form in many cases due to defects associated with dangling bonds. Scattering happens because after trapping a charge, the defect becomes charged and therefore starts interacting with free carriers. If scattered carriers are in the inversion layer at the interface, the reduced dimensionality of the carriers makes the case differ from the case of bulk impurity scattering as carriers move only in two dimensions. Interfacial roughness also causes short-range scattering limiting the mobility of quasi-two-dimensional electrons at the interface.
9600_15	Lattice (phonon) scattering At any temperature above absolute zero, the vibrating atoms create pressure (acoustic) waves in the crystal, which are termed phonons. Like electrons, phonons can be considered to be particles. A phonon can interact (collide) with an electron (or hole) and scatter it. At higher temperature, there are more phonons, and thus increased electron scattering, which tends to reduce mobility. Piezoelectric scattering Piezoelectric effect can occur only in compound semiconductor due to their polar nature. It is small in most semiconductors but may lead to local electric fields that cause scattering of carriers by deflecting them, this effect is important mainly at low temperatures where other scattering mechanisms are weak. These electric fields arise from the distortion of the basic unit cell as strain is applied in certain directions in the lattice.
9600_16	Surface roughness scattering Surface roughness scattering caused by interfacial disorder is short range scattering limiting the mobility of quasi-two-dimensional electrons at the interface. From high-resolution transmission electron micrographs, it has been determined that the interface is not abrupt on the atomic level, but actual position of the interfacial plane varies one or two atomic layers along the surface. These variations are random and cause fluctuations of the energy levels at the interface, which then causes scattering.
9600_17	Alloy scattering In compound (alloy) semiconductors, which many thermoelectric materials are, scattering caused by the perturbation of crystal potential due to the random positioning of substituting atom species in a relevant sublattice is known as alloy scattering. This can only happen in ternary or higher alloys as their crystal structure forms by randomly replacing some atoms in one of the sublattices (sublattice) of the crystal structure. Generally, this phenomenon is quite weak but in certain materials or circumstances, it can become dominant effect limiting conductivity. In bulk materials, interface scattering is usually ignored.
9600_18	Inelastic scattering During inelastic scattering processes, significant energy exchange happens. As with elastic phonon scattering also in the inelastic case, the potential arises from energy band deformations caused by atomic vibrations. Optical phonons causing inelastic scattering usually have the energy in the range 30-50 meV, for comparison energies of acoustic phonon are typically less than 1 meV but some might have energy in order of 10 meV. There is significant change in carrier energy during the scattering process. Optical or high-energy acoustic phonons can also cause intervalley or interband scattering, which means that scattering is not limited within single valley.
9600_19	Electron–electron scattering Due to the Pauli exclusion principle, electrons can be considered as non-interacting if their density does not exceed the value 1016~1017 cm−3 or electric field value 103 V/cm. However, significantly above these limits electron–electron scattering starts to dominate. Long range and nonlinearity of the Coulomb potential governing interactions between electrons make these interactions difficult to deal with. Relation between mobility and scattering time A simple model gives the approximate relation between scattering time (average time between scattering events) and mobility. It is assumed that after each scattering event, the carrier's motion is randomized, so it has zero average velocity. After that, it accelerates uniformly in the electric field, until it scatters again. The resulting average drift mobility is: where q is the elementary charge, m* is the carrier effective mass, and is the average scattering time.
9600_20	If the effective mass is anisotropic (direction-dependent), m* is the effective mass in the direction of the electric field. Matthiessen's rule Normally, more than one source of scattering is present, for example both impurities and lattice phonons. It is normally a very good approximation to combine their influences using "Matthiessen's Rule" (developed from work by Augustus Matthiessen in 1864): where µ is the actual mobility, is the mobility that the material would have if there was impurity scattering but no other source of scattering, and is the mobility that the material would have if there was lattice phonon scattering but no other source of scattering. Other terms may be added for other scattering sources, for example Matthiessen's rule can also be stated in terms of the scattering time: where τ is the true average scattering time and τimpurities is the scattering time if there was impurity scattering but no other source of scattering, etc.
9600_21	Matthiessen's rule is an approximation and is not universally valid. This rule is not valid if the factors affecting the mobility depend on each other, because individual scattering probabilities cannot be summed unless they are independent of each other. The average free time of flight of a carrier and therefore the relaxation time is inversely proportional to the scattering probability. For example, lattice scattering alters the average electron velocity (in the electric-field direction), which in turn alters the tendency to scatter off impurities. There are more complicated formulas that attempt to take these effects into account. Temperature dependence of mobility
9600_22	With increasing temperature, phonon concentration increases and causes increased scattering. Thus lattice scattering lowers the carrier mobility more and more at higher temperature. Theoretical calculations reveal that the mobility in non-polar semiconductors, such as silicon and germanium, is dominated by acoustic phonon interaction. The resulting mobility is expected to be proportional to T −3/2, while the mobility due to optical phonon scattering only is expected to be proportional to T −1/2. Experimentally, values of the temperature dependence of the mobility in Si, Ge and GaAs are listed in table.
9600_23	As , where is the scattering cross section for electrons and holes at a scattering center and is a thermal average (Boltzmann statistics) over all electron or hole velocities in the lower conduction band or upper valence band, temperature dependence of the mobility can be determined. In here, the following definition for the scattering cross section is used: number of particles scattered into solid angle dΩ per unit time divided by number of particles per area per time (incident intensity), which comes from classical mechanics. As Boltzmann statistics are valid for semiconductors .
9600_24	For scattering from acoustic phonons, for temperatures well above Debye temperature, the estimated cross section Σph is determined from the square of the average vibrational amplitude of a phonon to be proportional to T. The scattering from charged defects (ionized donors or acceptors) leads to the cross section . This formula is the scattering cross section for "Rutherford scattering", where a point charge (carrier) moves past another point charge (defect) experiencing Coulomb interaction. The temperature dependencies of these two scattering mechanism in semiconductors can be determined by combining formulas for τ, Σ and , to be for scattering from acoustic phonons and from charged defects . The effect of ionized impurity scattering, however, decreases with increasing temperature because the average thermal speeds of the carriers are increased. Thus, the carriers spend less time near an ionized impurity as they pass and the scattering effect of the ions is thus reduced.
9600_25	These two effects operate simultaneously on the carriers through Matthiessen's rule. At lower temperatures, ionized impurity scattering dominates, while at higher temperatures, phonon scattering dominates, and the actual mobility reaches a maximum at an intermediate temperature. Disordered Semiconductors While in crystalline materials electrons can be described by wavefunctions extended over the entire solid, this is not the case in systems with appreciable structural disorder, such as polycrystalline or amorphous semiconductors. Anderson suggested that beyond a critical value of structural disorder, electron states would be localized. Localized states are described as being confined to finite region of real space, normalizable, and not contributing to transport. Extended states are spread over the extent of the material, not normalizable, and contribute to transport. Unlike crystalline semiconductors, mobility generally increases with temperature in disordered semiconductors.
9600_26	Multiple Trapping and Release Mott later developed the concept of a mobility edge. This is an energy , above which electrons undergo a transition from localized to delocalized states. In this description, termed multiple trapping and release, electrons are only able to travel when in extended states, and are constantly being trapped in, and re-released from, the lower energy localized states. Because the probability of an electron being released from a trap depends on its thermal energy, mobility can be described by an Arrhenius relationship in such a system: where is a mobility prefactor, is activation energy, is the Boltzmann Constant, and is temperature. The activation energy is typically evaluated by measuring mobility as a function of temperature. The Urbach Energy can be used as a proxy for activation energy in some systems.
9600_27	Variable Range Hopping At low temperature, or in system with a large degree of structural disorder (such as fully amorphous systems), electrons cannot access delocalized states. In such a system, electrons can only travel by tunnelling for one site to another, in a process called variable range hopping. In the original theory of variable range hopping, as developed by Mott and Davis, the probability , of an electron hopping from one site , to another site , depends on their separation in space , and their separation in energy . Here is a prefactor associated with the phonon frequency in the material, and is the wavefunction overlap parameter. The mobility in a system governed by variable range hopping can be shown to be: where is a mobility prefactor, is a parameter (with dimensions of temperature) that quantifies the width of localized states, and is the dimensionality of the system. Measurement of semiconductor mobility Hall mobility
9600_28	Carrier mobility is most commonly measured using the Hall effect. The result of the measurement is called the "Hall mobility" (meaning "mobility inferred from a Hall-effect measurement"). Consider a semiconductor sample with a rectangular cross section as shown in the figures, a current is flowing in the x-direction and a magnetic field is applied in the z-direction. The resulting Lorentz force will accelerate the electrons (n-type materials) or holes (p-type materials) in the (−y) direction, according to the right hand rule and set up an electric field ξy. As a result there is a voltage across the sample, which can be measured with a high-impedance voltmeter. This voltage, VH, is called the Hall voltage. VH is negative for n-type material and positive for p-type material. Mathematically, the Lorentz force acting on a charge q is given by For electrons: For holes:
9600_29	In steady state this force is balanced by the force set up by the Hall voltage, so that there is no net force on the carriers in the y direction. For electron, For electrons, the field points in the −y direction, and for holes, it points in the +y direction. The electron current I is given by . Sub vx into the expression for ξy, where RHn is the Hall coefficient for electron, and is defined as Since Similarly, for holes From the Hall coefficient, we can obtain the carrier mobility as follows: Similarly, Here the value of VHp (Hall voltage), t (sample thickness), I (current) and B (magnetic field) can be measured directly, and the conductivities σn or σp are either known or can be obtained from measuring the resistivity. Field-effect mobility The mobility can also be measured using a field-effect transistor (FET). The result of the measurement is called the "field-effect mobility" (meaning "mobility inferred from a field-effect measurement").
9600_30	The measurement can work in two ways: From saturation-mode measurements, or linear-region measurements. (See MOSFET for a description of the different modes or regions of operation.) Using saturation mode In this technique, for each fixed gate voltage VGS, the drain-source voltage VDS is increased until the current ID saturates. Next, the square root of this saturated current is plotted against the gate voltage, and the slope msat is measured. Then the mobility is: where L and W are the length and width of the channel and Ci is the gate insulator capacitance per unit area. This equation comes from the approximate equation for a MOSFET in saturation mode: where Vth is the threshold voltage. This approximation ignores the Early effect (channel length modulation), among other things. In practice, this technique may underestimate the true mobility.
9600_31	Using the linear region In this technique, the transistor is operated in the linear region (or "ohmic mode"), where VDS is small and with slope mlin. Then the mobility is: This equation comes from the approximate equation for a MOSFET in the linear region: In practice, this technique may overestimate the true mobility, because if VDS is not small enough and VG is not large enough, the MOSFET may not stay in the linear region. Optical mobility Electron mobility may be determined from non-contact laser photo-reflectance technique measurements. A series of photo-reflectance measurements are made as the sample is stepped through focus. The electron diffusion length and recombination time are determined by a regressive fit to the data. Then the Einstein relation is used to calculate the mobility.
9600_32	Terahertz mobility Electron mobility can be calculated from time-resolved terahertz probe measurement. Femtosecond laser pulses excite the semiconductor and the resulting photoconductivity is measured using a terahertz probe, which detects changes in the terahertz electric field. Time resolved microwave conductivity (TRMC) A proxy for charge carrier mobility can be evaluated using time-resolved microwave conductivity (TRMC). A pulsed optical laser is used to create electrons and holes in a semiconductor, which are then detected as an increase in photoconductance. With knowledge of the sample absorbance, dimensions, and incident laser fluence, the parameter can be evaluated, where is the carrier generation yield (between 0 and 1), is the electron mobility and is the hole mobility. has the same dimensions as mobility, but carrier type (electron or hole) is obscured.
9600_33	Doping concentration dependence in heavily-doped silicon The charge carriers in semiconductors are electrons and holes. Their numbers are controlled by the concentrations of impurity elements, i.e. doping concentration. Thus doping concentration has great influence on carrier mobility. While there is considerable scatter in the experimental data, for noncompensated material (no counter doping) for heavily doped substrates (i.e. and up), the mobility in silicon is often characterized by the empirical relationship: where N is the doping concentration (either ND or NA), and Nref and α are fitting parameters. At room temperature, the above equation becomes: Majority carriers: Minority carriers: These equations apply only to silicon, and only under low field. See also Speed of electricity References
9600_34	External links semiconductor glossary entry for electron mobility Resistivity and Mobility Calculator from the BYU Cleanroom Online lecture- Mobility from an atomistic point of view Physical quantities Condensed matter physics Materials science Semiconductors Electric and magnetic fields in matter MOSFETs
9601_0	The Boeing 747-400 is a wide-body airliner produced by Boeing Commercial Airplanes, an advanced variant of the initial Boeing 747. The "Advanced Series 300" was announced at the September 1984 Farnborough Airshow, targeting a 10% cost reduction with more efficient engines and more range. Northwest Airlines (NWA) became the first customer with an order for 10 aircraft on October 22, 1985. The first 747-400 was rolled out on January 26, 1988, and made its maiden flight on April 29, 1988. Type certification was received on January 9, 1989, and it entered service with NWA on February 9, 1989.
9601_1	It retains the 747 airframe, including the 747-300 stretched upper deck, with winglets. The 747-400 offers a choice of improved turbofans: the Pratt & Whitney PW4000, General Electric CF6-80C2 or Rolls-Royce RB211-524G/H. Its two-crew glass cockpit dispenses with the need for a flight engineer. It typically accommodates 416 passengers in a three-class layout over a 7,285 nmi (13,490) km range with its MTOW.
9601_2	The first -400M combi was rolled out in June 1989. The -400D Domestic for the Japanese market, without winglets, entered service on October 22, 1991. The -400F cargo variant, without the stretched upper deck, was first delivered in May 1993. With an increased MTOW of , the extended range version entered service in October 2002 as the -400ERF freighter and the -400ER passenger version the following month. Several 747-400 aircraft have undergone freighter conversion or other modifications to serve as transports of heads of state, YAL-1 laser testbed, engine testbed or the Cosmic Girl air launcher. The Dreamlifter is an outsize cargo conversion designed to move Dreamliner components.
9601_3	With 694 delivered over the course of 20 years from 1989 to 2009, it was the best-selling 747 variant. Its closest competitors were the smaller McDonnell Douglas MD-11 trijet and Airbus A340 quadjet. It has been superseded by the stretched and improved Boeing 747-8, introduced in October 2011. In the late 2010s, older 747-400 passenger aircraft were being phased out by airlines in favor of long-range, wide-body twin engine aircraft, such as the Boeing 777, 787, and Airbus A350. In 2021, China Airlines celebrated the retirement of its final passenger 747-400, which was also amongst the last delivered aircraft sixteen years earlier. Development Background
9601_4	Following its introduction in 1969, the Boeing 747 became a major success with airlines and the flying public. As the world's first wide-body jetliner, the 747 had revolutionized air travel, and cemented its manufacturer's dominance in the passenger aircraft market. In 1980, Boeing announced the 747-300, its latest 747 variant featuring greater passenger capacity. This was made possible by making a stretched upper deck (SUD), previously an option on the 747-200, a standard feature. The SUD was almost twice as long as the original 747 upper deck. Besides increased capacity, the 747-300 did not offer any increase in range, nor did it include improvements in flight deck technology or construction materials. At the same time, 747s were becoming more costly to operate due to a number of factors, notably conventional flight control systems, three-person flight crews, and fuel costs.
9601_5	In 1982, Boeing introduced a two-crew glass cockpit, new engines, and advanced materials on its 757 and 767 twinjets. At the same time, combined sales of the 747-100, −200, −300, and 747SP models (collectively referred to as the 747 "Classics") exceeded 700, but new orders slowed precipitously. The introduction of the 747-300 did little to stem the decline, and itself faced potential competition from more modern designs. As a result, Boeing began considering a more significant upgrade for its largest passenger jet.
9601_6	By early 1984, company officials had identified five development objectives for the latest 747 upgrade: new technologies, an enhanced interior, a range increase, more efficient engines, and a 10 percent reduction in operating cost. In September 1984, Boeing announced development of the newest 747 derivative, the "Advanced Series 300", at the Farnborough Airshow. On October 22, 1985, the type was officially launched when Northwest Airlines became the first 747-400 customer, with an order for 10 aircraft. Cathay Pacific, KLM, Lufthansa, Singapore Airlines, and British Airways also announced orders several months later, followed by United Airlines, Air France, and Japan Airlines. Design effort
9601_7	Seven early customers, namely British Airways, Cathay Pacific, KLM, Lufthansa, Northwest, Qantas and Singapore Airlines, formed a consultative group to advise Boeing on the 747-400's design process. While the aircraft was planned as a new-technology upgrade, Boeing originally proposed minimal design changes in order to reduce development cost and retain commonality with existing models. The airline consultative group sought more advanced changes, including a two-crew glass cockpit. As a result of airline input, the 747-400's new digital cockpit design featured cathode-ray tube (CRT) display technologies first employed on the 757 and 767. The autopilot was also changed to that of the 757 and 767; on the 747-400 a software update was added to allow an 'altitude intervention' mode.
9601_8	The 747-400's wingspan was stretched by over the Classic 747 through wingtip extensions. For reduced aerodynamic drag, the wings were fitted with -tall winglets. Despite the added length, the wings were lighter as a result of new aluminum alloys. The horizontal tail was also redesigned to fit a fuel tank, resulting in a range increase, and the rudder travel was increased to 30 degrees. The landing gear was redesigned with larger wheels and carbon brakes. Internal changes further included a restyled cabin with new materials and updated fittings.
9601_9	New engines offered on the 747-400 included the Pratt & Whitney PW4056, the General Electric CF6-80C2B1F, and the Rolls-Royce RB211-524G/H. The engines offered lower fuel consumption and greater thrust, along with a full-authority digital engine control (FADEC) which adjusted engine performance for improved efficiency compared with the Classic 747s. A new auxiliary power unit (APU) manufactured by Pratt & Whitney Canada was also selected to provide on-ground power for the 747-400, with a 40 percent reduction in fuel consumption compared to previous APU designs.
9601_10	Production and testing Final assembly of the first 747-400 began at Boeing's Everett factory, the longtime site of 747 production, in September 1987. More than fifty percent of the aircraft was produced by subcontractors, with major structures, engine nacelles, and sub-assemblies supplied by Northrop, and upper deck fuselage frames from Daewoo. All components were integrated during the final assembly process at the Everett factory. The first aircraft, equipped with PW4056 engines, was completed over the winter months of late 1987. On January 26, 1988, the first 747-400 rolled out at the Everett factory, while the first 737-400 rolled out at Boeing's Renton factory on the same day, marking the first double jetliner rollout in the manufacturer's history. By the time of the rollout, the 747-400 program had amassed more than 100 orders.
9601_11	The 747-400 flew for the first time on April 29, 1988, under the command of test pilot James Loesch and co-pilot Kenneth Higgins. The first flight was six weeks behind schedule, owing to subcontractor delays in supplying components, and extra troubleshooting on the aircraft's electronics systems. The maiden flight took off from Paine Field, site of the Everett factory, and landed at Boeing Field, south of Seattle, after an uneventful 2 hours and 26 minutes. The 747-400's flight test program utilized the first four aircraft built, one more than the minimum number necessary to certify the aircraft's three engine options. One test aircraft each was fitted with the CF6-80C2B1F and RB211-524G/H engines, while the other two featured PW4056 engines, with the fourth aircraft serving as a backup. Federal Aviation Administration (FAA) certification was received on January 9, 1989, with Pratt & Whitney PW4000 engines, May 18, 1989 with General Electric CF6-80C2s and June 8, 1989 with Rolls-Royce
9601_12	RB211-524Gs.
9601_13	As the flight test program proceeded, Boeing encountered problems in the 747-400's production process, leading it to disclose delivery delays of up to one month for the first 20 aircraft built. A primary reason for the delays was the unprecedented complexity of interior configurations offered to airlines, which ranged from lavatory and galley locations to the color shades of cabin warning labels. Coupled with new, relatively inexperienced workers, a lack of veteran technicians, interior configurations needing costly re-work, and teething problems with electronics integration on the advanced flight deck, 747-400 production fell behind schedule. The company managed to resolve early production issues by mid-1989, with the first example airframes of all three engine variants delivered within four months of each other, and overall delays not exceeding several weeks. Service entry and operations
9601_14	The first 747-400 (N661US) was delivered to launch customer Northwest Airlines. This jet became known for an incident on Northwest Flight 85 caused by a rudder hardover. N661US was later sold to Delta Airlines when Northwest merged with it. N661US later became preserved at the Delta Flight Museum. This was the twentieth anniversary of the 747-100's first flight. On May 31, 1989, Singapore Airlines operated the first international service using a 747-400, on a flight from Singapore to London.
9601_15	In May 1989, one week before the initial delivery to the 747-400's first European customer, KLM, the Joint Aviation Authorities (JAA) shocked Boeing by refusing to grant regulatory certification for the aircraft, citing the upper deck cabin floor's resistance to collapse in the event of a sudden decompression. While the manufacturer asserted that the 747-400's cabin floor was no different from the already-certified and in-service 747-300, the JAA maintained that the newer model would have a service life into 2020 and beyond and was thus subject to a newer, more stringent standard which had been updated to reflect the risk of explosive devices. In the days leading up to the first delivery to KLM, negotiations between Boeing, the FAA, and the JAA resulted in a compromise: a temporary operating certificate would be issued for the 747-400, provided that the manufacturer develop a structural retrofit for the aircraft within two years. The last-minute deal allowed KLM and Lufthansa to take
9601_16	delivery of their 747-400s without further delays.
9601_17	After the first 747-400 deliveries, Boeing began production on more variants of the aircraft. The first 747-400 Combi, able to carry both passengers and freight, was rolled out in June 1989. The 747-400 Domestic, a short-range variant of the aircraft designed for Japanese intra-island services, first flew on March 18, 1991, and entered service with Japan Airlines on October 22, 1991. A cargo variant, the 747-400F, was first delivered in May 1993 to Cargolux. By the end of the 1990s, Boeing was producing four versions of the 747-400. Further developments
9601_18	The extended range freighter (ERF) entered service in October 2002. The next month, the extended range (ER) passenger version entered service with Qantas, the only airline ever to order the passenger version of the 747-400ER. Qantas initially used the 747-400ER for the Melbourne to Los Angeles and Dallas to Sydney route allowing the completion of the flight with full passenger load and cargo. Prior to the 747-400ER, Qantas would complete such flights by blocking out 'E' zone of the cabin and limiting passenger numbers and cargo. The 747-400ER featured the Boeing Signature Interior, which was later made available on the 747-400 (either as a retrofit on existing 747-400s or factory installation on new frames).
9601_19	The 747-400ER also introduced some flight deck enhancements, including liquid-crystal displays (LCDs), which replaced the six cathode ray tube (CRT) displays found on the Boeing 747-400. LCDs later became standard on the 747-400 as well, and could be retrofitted to earlier aircraft. The three standby flight displays found on the 747-400 were also replaced by a single combined LCD, the integrated standby flight display (ISFD), which also became standard on the 747-400 in late 2003.
9601_20	In the 2000s, as part of an effort to promote sustainable and alternative fuel development, as well as lower emissions, several 747-400 operators studied the use of oil extracted from the jatropha plant. Air New Zealand carried out the first commercial flight using jatropha oil for fuel; the airline's 747-400 had one engine burning a mix of 50% jatropha oil and 50% jet fuel for two hours during the flight while engineers collected data. Continental Airlines tested jatropha oil in one of its airliners on January 7, 2009. Jatropha is easy to grow, needs little fertilizer or water, and produces an oil-rich plant.
9601_21	In 2007, unit cost for the 747-400/-400ER was US$234 or 266.5 million, and for the 747-400F/-400ERF US$238 or 268 million. Production of the 747-400 passenger version officially ceased on March 15, 2007. The last four -400s on order were cancelled by Philippine Airlines (which switched to the 777-300ER). The last to order the -400 was China Airlines in November 2002, with the last passenger 747-400 constructed in 2005 and delivered in April of that year. It was the 1358th 747 (MSN33737/B-18215). The last 747-400 was a -400ERF delivered on December 22, 2009, to Kalitta Air.
9601_22	Retirement and economic value The 747-400's leasing, resale and salvage value has dropped steeply because it is relatively expensive to operate. As most 747-400s are now more than 20 years old, airlines are beginning to replace them. Airlines using the 747-400 have been retiring the model, replacing it with more fuel efficient aircraft. The main appeal of the 747-400 like its predecessors was its range rather than its capacity, and in most cases it has been replaced by wide-body twin-engine aircraft of similar range, such as the Boeing 777 and Boeing 787 Dreamliner. The change in emphasis from hub and spoke operations to point-to-point flights has also reduced the need for jumbo jets. Airlines such as British Airways and Qantas that plan to maintain the same capacity on routes currently served by 747-400s ordered the Airbus A380 rather than the updated 747-8.
9601_23	For example, Delta Air Lines reduced the number of flights it operated from the United States to Narita International Airport that were intended to transfer passengers to other destinations in Asia, switching to twin-engine widebody aircraft operating from an expanded hub at Seattle-Tacoma International Airport. Total capacity was cut, but load factors improved. In April 2015, Delta announced it would accelerate the retirement of its 747-400s and replace them either with Airbus A330 or Airbus A350 aircraft (both of which are twinjets). Delta could not keep the 747s full without deeply discounting ticket prices; the discounts and increased maintenance required of a four-engine aircraft led to a drag on profits.
9601_24	Since the cost of replacing a 747-400 is high (an airline must purchase or lease another wide-body), some operators choose to fly the 747-400 to the conclusion of its accepted useful life and then scrap it. The current parts resale value for this aircraft has been reduced to its engines. When a 26-year-old 747-400 owned by Delta flew through a violent hailstorm, the company indicated it was likely the aircraft would be scrapped. George Dimitroff, head of valuations for FlightGlobal, estimated the aircraft's value before the incident at about $8 million. He noted that this was not the same as its insured value. As discussed in the section on 747-400 converted freighters, there is no longer a viable economic model for converting retired passenger 747-400 aircraft into dedicated freighters, so most retired passenger aircraft will likely be scrapped.
9601_25	Several airlines have retired their 747-400s from the trans-pacific market. Remaining operators in 2014 included EVA Air, Qantas, Virgin Atlantic, British Airways and United. United's deployment of them also reflected a change in emphasis from Asian hubs to domestic hubs. On January 11, 2017, United announced it would begin phasing out its 747-400s and made its last 747 flight on November 7 that year. Delta Airlines was the last US airline to operate the Boeing 747, retiring the last of the 747-400 fleet it inherited from Northwest Airlines in December 2017. British Airways, the largest passenger 747-400 operator, announced that they will be phasing out their 747-400 fleet in February 2024, British Airways will replace its Boeing 747-400s with the Airbus A350-1000. Lufthansa will be retiring their 747-400 fleet in 2025 as they are being replaced by the Boeing 777x and the Boeing 747-8i. KLM will be retiring their 747-400 Combi and Passenger fleet in 2020 as they are being replaced by
9601_26	the Boeing 777-300ER, the Boeing 787-10 Dreamliner, and the Airbus A350-900. However, KLM announced it plans to retire its last Boeing 747-400 by January 1, 2021 instead of 2020 due to delivery delays for the new wide-body twin jets.
9601_27	The global COVID-19 pandemic hastened the retirement of many remaining passenger Boeing 747-400s due to a sharp decline in passenger traffic. For instance, KLM retired its Boeing 747-400 Combi and Passenger fleets in March 2020. Qantas announced the retirement of its 747-400 and 747-400ER fleet by the end of 2020, with the Boeing 787-9 Dreamliner taking its place. China Airlines also announced that they will be retiring their remaining four passenger Boeing 747-400s by the end of 2020 due to the COVID-19 pandemic (which were delivered between 2004 and 2005, operating on flights within Asia) with the Airbus A350-900 and Boeing 777-300ER taking over all high-volume routes and all Asian International routes. However, China Airlines didn't retire its last passenger Boeing 747-400 until February 2021. British Airways retired its remaining 31 Boeing 747-400s 4 years ahead of the original February 2024 deadline. Virgin Atlantic also retired their remaining leisure fleet 747-400s in May 2020
9601_28	citing the COVID-19 pandemic - the fleet was due to retire in 2021. As of September, 2021, there were just 42 passenger 747-400 in operation (10 actively flying, 32 in storage) across 10 carriers worldwide. Lufthansa and Air China had plans to resume flying some of their stored aircraft by October, 2021.
9601_29	Design The 747-400's airframe features extended and lighter wings than the previous 747s, capped by winglets. The winglets result in a 3 percent increase in long-range cruise, improved takeoff performance, and higher cruise altitudes. The extended wingspan also gains an additional leading edge flap section. When unfurnished, the basic 747-400 fuselage is lighter than preceding models, but when fitted out it is heavier and stronger than previous models. The landing gear uses the same configuration as the previous 747s, but with carbon brakes replacing the previous steel ones, and overall weight savings of .
9601_30	The 747-400's glass cockpit features CRT displays which show flight instrumentation along with engine indication and crew alerting system (EICAS) diagnostics. The flight engineer station on the previous 747s is no longer installed, and the new displays and simplified layout results in a two-thirds reduction of switches, lights, and gauges versus the Classic 747. Other new systems include an advanced Honeywell flight management computer (FMC) which assists pilots in calculating optimal altitudes and routes along with a Rockwell-Collins central maintenance computer (CMC) which automates troubleshooting tasks.
9601_31	The redesigned 747-400 interior features new cabin sidewalls, heat-resistant phenolic glass, carbon composite paneling, and larger storage bins. An enhanced in-flight entertainment framework, called the Advanced Cabin Entertainment/Service System (ACESS), debuted on the 747-400, which integrates 18-channel audio capability, four-passenger intercom announcement zones, inter-cabin telephones, and passenger lighting into a central system. An eight-bunk overhead crew rest is installed above the aft cabin, while a second crew rest area is located on the upper deck behind the cockpit for flight crew use. The last few 747-400s delivered feature the Boeing Signature Interior, derived from the Boeing 777. Variants 747-400
9601_32	The original variant of the redesigned 747, the 747-400 debuted an increased wingspan, winglets, revised engines, and a glass cockpit which removed the need for a flight engineer. The type also featured the stretched upper deck (SUD) introduced with the 747-300. The passenger model formed the bulk of 747-400s sold, and 442 were built.
9601_33	In 1989, the Qantas 747-400 VH-OJA flew non-stop from London Heathrow to Sydney, a distance of , in 20 hours and 9 minutes to set a commercial aircraft world distance record. , this is the fastest heavyweight flight between London and Sydney. This was a delivery flight with no commercial passengers or freight on board. During testing, the first 747-400 built also set a world record for the heaviest airliner takeoff on June 27, 1988, on a flight to simulate heavy-weight stalls. The aircraft had a takeoff weight of , and in order to satisfy Fédération Aéronautique Internationale regulations, climbed to a height of . On February 9, 2020, a British Airways Boeing 747-400 broke the New York–London subsonic airliner speed record in 4 hours 56 minutes, pushed by the powerful Jetstream linked to Storm Ciara. 747-400F
9601_34	The 747-400F (Freighter) is an all freight version of the 747-400. While using the updated systems and wing design of the passenger versions, it features the original short upper deck found on the classic 747s to reduce weight. The 747-400F has a maximum takeoff weight of and a maximum payload of . The -400F can be easily distinguished from the passenger -400 by its shorter upper-deck hump and lack of windows along the main deck. The model's first flight was on May 4, 1993, and entered service with Cargolux on November 17, 1993. Major customers included Atlas Air, Cargolux, China Airlines, Korean Air, Nippon Cargo Airlines and Singapore Airlines.
9601_35	The 747-400F has a main deck nose door and a mechanized cargo handling system. The nose door swings up so that pallets or containers up to can be loaded straight in on motor-driven rollers. An optional main deck side cargo door (like the 747-400M Combi) allows loading of dimensionally taller cargo modules. A lower deck ("belly") side door allows loading of unit load devices (ULD) up to 163 cm in height. Boeing delivered 126 Boeing 747-400F aircraft with no unfilled orders . The last -400F was delivered to Nippon Cargo Airlines on August 2, 2008. A 2008 747-400F value new was $ million, a 2003 aircraft was leased $400,000 per month in 2019 for a $29 million value while a B747-400BCF was priced at around $10 million. 747-400M
9601_36	The 747-400M (a passenger/freight or "Combi" variant originally designated as 747-400BC) first flew on June 30, 1989, and entered service with KLM on September 12, 1989. Based on the successful Combi versions of the Classic 747s, the -400M has a large cargo door fitted to the rear of the fuselage for freight loading to the aft main deck cargo hold. A locked partition separates the cargo area from the forward passenger cabin, and the -400M also features additional fire protection, a strengthened main deck floor, a roller-conveyor system, and passenger-to-cargo conversion equipment. The last 747-400M was delivered to KLM on April 10, 2002. Boeing sold 61 747-400M aircraft, which was similar to earlier 747 "Combi" versions (78 747-200M, 21 747-300M).
9601_37	KLM is the last 747-400M operator. The Boeing 747-400M was initially planned to be retired by January 1, 2021, however the Boeing 747-400M was instead retired by March 27, 2020, as Air France-KLM announced in early March 2020 to retire all remaining passenger Boeing 747-400s of KLM (including all KLM Boeing 747-400M aircraft) immediately due to reduced air travel demand caused by the COVID-19 pandemic, although, due to a global shortage in air cargo capacity, three KLM 747-400Ms were temporarily reactivated after just a week to operate cargo-only flights to Asia. 747-400D The 747-400D (Domestic) is a high-density seating model developed for short-haul, high-volume domestic Japanese flights, serving the same role as the prior Boeing 747-100SR domestic model. This model is capable of seating a maximum of 568 passengers in a two-class configuration or 660 passengers in a single-class configuration.
9601_38	The -400D lacks the wingtip extensions and winglets included on other variants. Winglets would provide minimal benefits on short-haul routes while adding extra weight and cost. The -400D may be converted to the long-range version if needed. The 747-400D can be distinguished from the otherwise similar-looking 747-300 by the extra windows on the upper deck. These allow for extra seating at the rear of the upper deck, where a galley would normally be situated on longer flights. In total, 19 of the type were built, with the last example delivered to All Nippon Airways on February 11, 1996. This variant was retired when ANA retired its last 747-400D on March 31, 2014. 747-400ER
9601_39	The 747-400ER (Extended Range) was launched on November 28, 2000, following an order by Qantas for six aircraft. The model was commonly referred to as the '910k' signifying its maximum weight achieved via structural modifications and modified landing gear. The 747-400ER included the option of one or two additional body fuel tanks in the forward cargo hold, however, Qantas was the only customer that ordered the single body tank configuration, and no airplanes were delivered with dual body fuel tanks. Manufactured by Marshall Aerospace, these tanks utilized metal to metal honeycomb-bonded technology to achieve a high fuel volume-to-dry weight ratio. The tanks feature a double wall, integrated venting system, and achieve fuel control via a modified Fuel System Management Card (FSMC) which optimizes fuel transfer into the Center Wing Tank (CWT) in flight along with the fuel transfer from the Horizontal Stabiliser Tank (HST). The tank is removable using tooling that interfaces with the
9601_40	cargo loading system. Similar technology has been used by Marshall in the development of body fuel tanks for the Boeing 777-200LR and Boeing P-8A Poseidon. Other changes to the 747-400ER include the relocation of oxygen system components and the potable water system tanks and pumps, since the body fuel tanks prevent access to the standard locations.
9601_41	The first 747-400ER was used as a test flight airplane and painted in Boeing colors, registration N747ER. Qantas received the first delivery of a 747-400ER registration VH-OEF on October 31, 2002; however, this was the second airplane built. The flight test airplane was later refurbished, repainted in standard QANTAS livery, and registered as VH-OEE. Qantas was the only customer for the passenger version of the 747-400ER, chosen by the airline to allow for full loads between Melbourne and Los Angeles, particularly in the western direction. The 747-400ER can fly farther, or carry more payload, than the -400. In May 2018 Qantas announced that it would retire its entire 747 fleet including all 747-400ERs by 2020. 747-400ERF
9601_42	The 747-400ERF (Extended Range Freighter) is the freight version of the -400ER, launched on April 30, 2001. The 747-400ERF is similar to the 747-400F, except for increased gross weight capability which allows it to carry more payload. Unlike the 747-400ER, no customers ordered the optional body (cargo compartment) fuel tanks which reflects the desire to carry more cargo, not fuel, as the benefit of the improved payload rating. The 747-400ERF has a maximum takeoff weight of and a maximum payload of . It offers cargo airlines the choice of either adding more payload than other 747-400 freighter variants, or adding to the maximum range.
9601_43	The -400ERF has a range of with maximum payload, about farther than the standard 747-400 freighter, and has a strengthened fuselage, landing gear, and parts of its wing, along with new, larger tires. The first -400ERF was delivered to Air France (via ILFC) on October 17, 2002. Boeing has delivered 40 Boeing 747-400ERFs with no outstanding orders. The new 747-8 Freighter has more payload capacity, but less range than the 747-400ERF when both are at MTOW. 747-400 Boeing Converted Freighter The 747-400BCF (Boeing Converted Freighter), formerly known as the 747-400SF (Special Freighter), is a conversion program for standard passenger 747-400s. The project was launched in 2004 with conversions by approved contractors such as HAECO, KAL Aerospace and SIA Engineering Company. The first Boeing 747-400BCF was redelivered to Cathay Pacific Cargo and entered service on December 20, 2005. Cathay retired the 747-400BCF in 2017 after 11 years of service.
9601_44	The 747-400BDSF (BeDek Special Freighter) is another passenger-to-freighter conversion, carried out by Israel Aerospace Industries (IAI). The first 747-400BDSF was redelivered to Air China Cargo in August, 2006. Several Boeing 747-400Ms of EVA Air have been converted as BDSF model after retiring from passenger service. Neither the 747-400BCF nor the 747-400BDSF has a nose cargo door; freight can only be loaded through the side cargo door.
9601_45	The demand for converted 747-400 freighters declined in the early 2010's, due to the availability of belly cargo capacity on more efficient passenger wide-body twin jets, and new orders for Boeing 747-8F and 777F freighters. Approximately 79 747-400 aircraft were converted before the programs were terminated; 50 of these converted aircraft were 747-400BCF, with the remaining 29 being 747-400BDSF. Boeing announced the end of their conversion program in 2016, although conversions had ceased years earlier with no orders after 2012. Some converted freighters, that had been retired to desert storage, were returned to active service due to the increase in demand for air cargo capacity in the 2020-2021 COVID era. 747 Large Cargo Freighter
9601_46	Boeing announced in October 2003 that, because of the amount of time involved with marine shipping, air transport would be the primary method of transporting parts for the Boeing 787 Dreamliner. Used passenger 747-400 aircraft have been converted into an outsize, "Large Cargo Freighter" (LCF) configuration to ferry sub-assemblies to Everett, Washington for final assembly. The LCF has a bulging fuselage similar to that of the Aero Spacelines Super Guppy or Airbus Beluga cargo aircraft. The conversion, designed by Boeing engineers from Puget Sound, Moscow and Canoga Park, Cal., and Gamesa Aeronáutica in Spain, was carried out in Taiwan by a subsidiary of the Evergreen Group. Boeing purchased four second-hand aircraft and had them all converted; the fourth and final LCF took its first flight in January 2010.
9601_47	Delivery times are as low as one day using the 747 LCF, compared to up to 30 days for deliveries by ship. The LCF had the largest cargo hold of any aircraft until being surpassed by the Airbus Beluga XL, and can hold three times the volume of a 747-400F freighter. The LCF is not a Boeing production model and has not been offered for sale to any customers. The LCFs are intended for Boeing's exclusive use.
9601_48	Government, military and other variants C-33: Proposed U.S. military transport version of the 747-400F, intended to augment the Boeing C-17 Globemaster III fleet. The C-33 cost less and had greater range, although it could not use austere runways or handle outsize military equipment and had a higher expected operating cost. The plan was canceled in favor of the purchase of more C-17s. KC-33: Proposed US military tanker version of the 747-400BCF. YAL-1: "Airborne Laser" carrier based on a 747-400F for the United States Air Force. The aircraft was heavily modified to carry a nose-mounted turret and Chemical Oxygen Iodine Laser (COIL) equipment in order to destroy Intercontinental Ballistic Missiles. The aircraft was retired in 2012 after cancellation of the program funding. A number of other governments also use the 747-400 as a VIP transport, including Bahrain, Brunei, India, Japan, Oman, Qatar, Saudi Arabia and United Arab Emirates.
9601_49	A former Virgin Atlantic 747-400 named Cosmic Girl is used by Virgin Galactic as the air launch to orbit launcher for LauncherOne, an orbital rocket. 747-400 Water Bomber: Global SuperTankers has converted an ex-Japan Airlines 747-400BCF for use as an airborne firefighter, serving as the second generation 747 Supertanker. The converted water bomber carries of water or chemical fire retardant in eight pressurized tanks. The United States Forest Service was considering the use of this aircraft in 2017. Global SuperTanker received FAA certification September 12, 2016.
9601_50	Operators As of January 2022, there are 41 passenger aircraft in service. The largest operator is Rossiya Airlines with nine. Additionally, there are 214 freighters in service, operated primarily by Atlas Air (36), Kalitta Air (24), China Airlines (18) and Cargolux(16). Former operators This list also includes carriers that used the aircraft temporarily, besides main operators. Commercial
9601_51	Aerolineas Argentinas Aerosur Air Canada Air Cargo Germany Air France Air Namibia Air New Zealand Air Pacific Al Wafeer Air Alitalia Cargo All Nippon Airways Ansett Australia Avianca Biman Bangladesh Airlines Blue Sky Airlines British Airways British Airways World Cargo Canadian Airlines Cargo B Airlines Cathay Pacific China Airlines Condor Corsair Delta Air Lines Dragonair Cargo Emirates SkyCargo Etihad Cargo EVA Air El Al Evergreen International Airlines Flynas Garuda Indonesia Global Supply Systems Grandstar Cargo Greatwall Airlines Iberia Jade Cargo International Japan Airlines Kenya Airways Cargo KLM Kuwait Airways Lion Air Lufthansa Cargo Malaysia Airlines Mandarin Airlines Northwest Airlines Olympic Airways Royal Air Maroc Oasis Hong Kong Airlines Philippine Airlines Phuket Airlines Qantas Sabena Saudia Singapore Airlines South African Airways Southern Air Surinam Airways TAAG Angola Airlines TAT Transaero
9601_52	Union de Transports Aériens United Airlines Varig Virgin Atlantic Wamos Air World Airways
9601_53	Non-commercial Government of Kuwait United States Air Force Deliveries Incidents and accidents
9601_54	The first hull loss of a 747-400 occurred on November 4, 1993, when China Airlines Flight 605, flying from Taipei to Hong Kong's Kai Tak Airport, touched down more than past the runway's displaced threshold during 20-knot (gusting to 38 knots) crosswinds. Combined with the disengagement of auto brakes and retracted speed brakes, manual braking and thrust reversal were not enough to prevent the aircraft from sliding into Victoria Harbour. No one was seriously injured, but the aircraft was written off. The type's second hull loss occurred on October 31, 2000, when Singapore Airlines Flight 006, a 747-400 flying on a Singapore to Los Angeles route via Taipei, rammed into construction equipment while attempting to take off from a closed runway at Chiang Kai-shek International Airport. The aircraft caught fire and was destroyed, killing 79 passengers and four crew members. The cause was attributed to the flight crew navigating to the wrong runway.

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