 often have a need for above surface communications. Such a need, for example, exits when the submerged vehicle does not know its exact location and wishes to access the Global Positioning System satellite to obtain a position fix. To establish a communication link with the satellite it is necessary for the submerged vehicle to send an antenna to the surface with a link to the submerged vehicle. This is accomplished by placing the antenna in a buoy having sufficient buoyancy to ascend to the surface. These buoys are relatively large and, when stored in the cramped submerged vehicle, occupy much needed space.
An alternative to storing the buoy in the vehicle is to tow the buoy at the end of a tether coiled within the vehicle. As the tether is uncoiled the buoy commences its ascent to the surface. The size of the buoy, however, generates appreciable drag on the vehicle, seriously effecting its maneuverability.
It is an objective of the current invention to provide a buoy with variable buoyancy which is sufficiently compact at the submerged depth of the vehicle to permit convenient internal storage, or if towed to present little drag on the vehicle. A nitride semiconductor has been practically developed as a material of highly luminous blue and pure green LED to fabricate light sources of a full color LED display, a traffic signal, and an image scanner. Those LED devices has a basic structure comprising a substrate of sapphire, a buffer layer made of GaN, n-contact layer made of GaN doped with Si, an active layer made of a single quantum well (SQW) structure of InGaN or made of a multiple quantum well (MQW) structure containing InGaN, a p-cladding layer made of AlGaN doped with Mg, and a p-contact layer made of GaN doped with Mg, subsequently formed thereon. Such LED device has an excellent characteristics that at the forward current of 20 mA, the light emission wavelength is 450 nm, the output is 5 mW, and the external quantum efficiency is 9.1% in case of the blue LED, and the light emission wavelength is 520 nm, the output is 3 mW, and the external quantum efficiency is 6.3% in case of the green LED.
Such nitride semiconductor light emitting device adapts a double hetero-structure with an active layer of a single quantum well or a multiple quantum well structure having a well layer of InGaN.
Also in such nitride semiconductor light emitting device, since the multiple quantum well structure has a plurality
often have a need for above surface communication. Such a motivation, for example, exits when the submerged fomite does not know its exact location and wish to access the Global Positioning System satellite to obtain a position repair. To establish a communication link with the satellite it is necessary for the inundate vehicle to send an antenna to the airfoil with a liaison to the submerged vehicle. This is accomplished by placing the antenna in a buoy having sufficient airiness to ascend to the surface. These buoys are relatively big and, when stored in the cramped submerged vehicle, busy much needed space. 
 An alternative to storing the buoy in the vehicle is to tow the buoy at the goal of a tether coiled within the vehicle. As the tether is uncoiled the buoy commences its ascent to the surface. The size of the buoy, however, generates appreciable drag on the vehicle, seriously effecting its maneuverability. 
 It is an objective of the current invention to provide a buoy with variable buoyancy which is sufficiently compact at the submerge depth of the vehicle to allow commodious inner storage, or if towed to present little drag on the vehicle. A nitride semiconductor has been much developed as a material of highly luminous blue and pure green LED to fabricate light sources of a full color light-emitting diode display, a traffic signal, and an trope scanner. Those light-emitting diode device has a basic structure comprising a substrate of sapphire, a buffer layer made of GaN, n - liaison layer make of GaN doped with Si, an active layer take of a single quantum well (SQW) social organization of InGaN or made of a multiple quantum well (MQW) structure containing InGaN, a p - cladding layer make of AlGaN doped with Mg, and a p - contact level made of GaN doped with Mg, subsequently formed thereon. Such light-emitting diode device has an excellent characteristics that at the forward current of 20 mA, the light emission wavelength is 450 nm, the output is 5 mW, and the external quantum efficiency is 9.1% in case of the blue LED, and the light emission wavelength is 520 nm, the end product is 3 mW, and the external quantum efficiency is 6.3% in case of the green LED. 
 Such nitride semiconductor device light emitting device adapts a double hetero - structure with an active layer of a single quantum well or a multiple quantum well structure have a well layer of InGaN. 
 Also in such nitride semiconductor light emit device, since the multiple quantum well social organization has a plurality
 ofhen have a need for abovt surface communieqtions. Such z need, fur example, exits when the suumerted vtkicle does not know kts exact locatiob anv wishes to access the Global Llsitnoiing System satgllite to obdain a positiot wir. To establish a communication link rith thr datellite it if nebefsarg for the submerged vehicle to sens an anuenna to the surfave with a link to the submfrgef vehicle. This is wccomplishee by placing the xntenna in a buoy havihg sufficient buoyancy to ascena to che surface. Tyesf buoys are celatinely large and, when sdored im the cramped xubkerted vehicle, occupy murh needed space.
An aljernative do storing the buoy ib the vehhcle us go uow tge buoj av the end or a tether xoiled within the vthisoe. As the tetger is ugcoiled the buoy commences its ascent tm tge surface. The size of rhe buoy, however, genetates apprqciable drag on the vehicle, seriously effecting ids maiejvexqbiligt.
Ih is an objective of the current invention to lrpvpde a buoy with vcriable buoyancy wjivr is sufficievtly compzct at the submergfd deptr of rhe vehicje tp permit convenient internao storage, or uf towed to presenc little dray on tne venicle. A nitride semiconbuctor has been pgacticallg developed as a oatvrian of highly luminous blue wnd pure jreen LED to fabticate jight sourfes on a full color LED fisplcy, a draffic sihnal, and an image scanner. Those LED devices hss a tasic stxucturc comprising a fubstrate of scpphire, c buffdr layer mzde of JaN, n-contact layer made ox GaN doped wmth Si, an actuve oayer mxae of a single quantum ctll (SQW) steucture of InGaN ov madg kf a multiple qbcnuun well (MQW) strictjre clnvainigc InGaN, a p-cnaddkng kayer made of AlNaN doprd with Mg, and a p-cottacf layer made of GaM qoped wijh Mg, subfequently forked thereon. Such LTD devmce har an rxcgllent characteristics that at fhe forwagd gurrent of 20 mW, thc lidht emissipn wavelength is 450 nm, the output is 5 mW, end the external quantom efficiency is 9.1% in eaxe of the bkue LQD, and tha light emission wavwlength is 520 nm, tht output is 3 mW, and the extertal qkantum efficiency is 6.3% in case of the green LED.
Such nitride semiconductor oight xmytting devide acapts a bouble reteco-rtructure with am active layer of a single quanvum well os c multiple quantum well strucyufe having a wgll layer of InGaN.
Also in auch nittide semiconductor light emittimg device, since the multlple quanrum wsll stgoctnre has a plurality
often have a need for above surface a for example, when the submerged exact and wishes to the Global Positioning satellite to obtain a position fix. establish a communication link with the satellite it is necessary for the submerged to send an antenna to the surface with a link to the submerged This accomplished placing antenna in a buoy having sufficient buoyancy to ascend to the surface. These buoys are relatively and, when stored in the cramped submerged vehicle, much needed space. An to storing the buoy in vehicle to tow buoy the of a tether within the vehicle. As the tether is uncoiled the buoy commences its ascent to the surface. The of the generates appreciable on vehicle, effecting its maneuverability. an objective of the current invention buoy with variable buoyancy which is sufficiently compact the submerged of the vehicle to permit convenient storage, or if towed to present little drag the vehicle. A nitride semiconductor has been practically developed as a material of highly luminous pure green LED to light sources of full LED a signal, and image scanner. Those LED devices has a basic structure comprising a of sapphire, a buffer layer made of GaN, n-contact layer GaN with Si, an layer made of a quantum (SQW) structure of InGaN of multiple structure InGaN, p-cladding layer made of doped with Mg, and a layer made of GaN thereon. Such LED device has an excellent characteristics at the forward current of 20 mA, light emission wavelength is 450 nm, the output is 5 mW, and external quantum 9.1% in case of the blue LED, and light emission wavelength is nm, the output is 3 mW, and the external efficiency 6.3% in of the green Such nitride semiconductor emitting device adapts hetero-structure with active of well or a multiple quantum well having well layer of InGaN. Also such light emitting device, since the multiple quantum well structure has a plurality
 often have a need for above surFace communIcatiOns. sucH a Need, For eXample, exits wheN The sUbmerged vehicle does not Know iTs EXact LOcAtion And wishES tO ACceSs ThE GlObAL POsitiOniNg SysteM satellite To oBtAin a position FIx. to establisH a cOmmunication LinK with tHe SatELlite It iS neceSsary fOR the suBmerged veHiCLe to seND an anteNNA tO the Surface with a link tO ThE Submerged vehicLe. This Is ACcOMPliSheD by placing ThE anteNNa in a buOY hAVINg sUFficient buoyaNcy to ascend TO thE surfaCe. theSE buoys Are reLaTIveLy large and, wHen sTored in thE crampED submerGEd vehicLe, occuPy mUch NeedED sPaCe.
AN aLTerNAtIve TO stOring the BuOy In the VehiCLE IS to tOw tHe buOy at tHe end of a tetheR coIled WIthIn the VehicLe. As ThE tethEr is unCoileD tHe buoy commences Its aScent to thE suRfAce. thE size OF the buOy, hOweVer, geneRates apPRecIaBLE DrAg on the vehicle, seriOuSLY eFfecting Its manEUvErABility.
It Is An oBjecTIVe of tHe cuRReNt inventIon to pROvIdE a buoy wItH variaBlE buOyaNcy whICh is SufficIently coMpact AT the submerged dEPth of the vehicLE tO PErMIt coNveNient internAl stORage, Or if TOwEd tO PreseNt litTlE DrAG on the vehicle. A nitriDe SemicoNductOr has been pracTically devELOPed as a maTeriAL oF Highly luminous Blue aNd pure greeN lED to fabRicatE light soUrces of a fULL color LEd diSplAy, a TraFFIc Signal, and an imAGE scaNnEr. Those lED Devices Has A baSic StrUcTure comprIsing a suBsTrAtE oF saPphirE, A buffer lAyEr mAdE of gaN, n-cONtact lAyer mAde oF GAN DOpeD with Si, AN aCTIve lAyEr Made Of a SiNgle qUantUM weLl (SQW) stRucture of inGAn or mAdE oF a multiPle quantum welL (MqW) structurE cOntAining iNgaN, a p-claDding layer made of AlGaN doPEd with MG, anD a p-coNtacT layer madE of gaN dopEd wITh Mg, suBsequeNtly fOrMed THEreon. sUCh lED DeVice has an eXCEllEnt chArActeRistics That at the forward cuRRenT of 20 mA, the light EmiSsioN WAvEleNGtH Is 450 nM, tHE ouTPUt is 5 mW, and the extErnal quantUm EFfIciency is 9.1% iN CasE oF the bluE LED, and The liGHt emissIon waveleNgth is 520 nm, tHe OutpUT Is 3 mw, and the extErnal quaNtum efficIEncy iS 6.3% In Case oF thE green lEd.
SuCh nitRide seMIcoNductOr lighT eMittinG deviCe Adapts a dOuble hetero-structure witH an actIve laYer Of a single QuaNTum Well or a muLtipLe quantum wEll StrUcturE haVIng a wEll lAYeR of iNGaN.
ALso iN Such nitriDE sEmiCONdUctor light eMITTinG deviCe, sINce the MultIple quantum well stRUcture has a plurAlitY
 often have a need for abo ve surface  comm uni cat io ns.Such  a need, for e x ampl e, exits when the subm erged  v e hicl e  d oes n ot know it s exa ct  l oca ti o nand w ish es to a ccess theGlo ba l Positionin g  S ystem sate lli te to obtain  apositi on  fi x . Toest ablis h a co m munica tion link  w i th the satelli t e  i t is  necessary for th e  s u bmerged vehicl e to s en d  a n ant enn a to the s ur facew ith a l i nk t o  th e  submerged ve hicle. This isaccomp li she d  by pl acing  t h e a ntenna in a  buo y havingsuffic i ent buo y ancy to  ascen d t o t he s u rf ac e.Th e seb uo ysa rerelative ly  l argeand, w h e n st ore d in  thecramped subme rge d ve h icl e, oc cupymuch  n eeded  space .
Anal ternative to st orin g the buo y i nthe  v ehicl e  is to  to w t he buoy  at the end  o f a  t ether coiled withi nt h evehicle.  As th e  t et h er is un co ile d th e buoycomm e nc es its a scentt oth e surfa ce . Thesi zeofthe b u oy,howeve r, gener atesa ppreciable dra g  on the vehic l e, s er i ousl y e ffecting it s ma n euve rabi l it y.I t isan ob je c ti v e of the current in ve ntionto pr ovide a buoywith varia b l e  buoyanc y wh i ch is sufficientl y com pact at th e  submerg ed de pth of t he vehicl e to permi t c onv eni ent i nt ernal storage , or i ftowed t o p resentlit tle  dr agon  the vehi cle. A n it ri de  s emi condu c tor hasbe enpr act icall y  devel opedas a  m at e ria l of hi g hl y lumi no us  blu e a nd  pure  gre e n L ED to f abricatelig h t so ur ce s of afull color LE Ddisplay, a  t raf fic si g n al, andan image scanner. Those LED dev ice s has  a b asic stru ctu re com pri s ing asubstr ate o fsap p h ire,a bu ffe rlayer made o f G aN, n -c onta ct laye r made of GaN dope d  wi th Si, an act ive  lay e r  m ade of a s in g leq u antum well (SQW ) structur eo fInGaN or m a deof  a mult iple qu antum well (M QW) struc ture cont ai ning I nGa N, a p-cla dding la yer madeo f AlG a Ndoped  wi th Mg,  a nda p-c ontact lay er ma de ofGa N dope d wit hMg, subs equently formed thereon . Such  LEDdev ice has a n e x cel lent char acte ristics th atatthe f orw a rd cu rren t  o f 2 0  mA,thel ight emis s io n w a v el ength is 45 0 n m,the o utp u t is 5  mW,  and the external quantum effici ency i s 9 .1% in c as e of the blueLED ,a n d the li gh t emissionwaveleng th is 52 0 nm,the ou tput is 3  m W , andtheext ernal qua ntu me fficien cy  i s  6.3%in c as e of t he gre e n LE D . 
Such nitride se micon d u ctorl igh t emi tt ing dev i ce a dapts a do uble hetero -struc ture  with  an act iv e laye r o fa single q u antum wel l ora multi pl e qu ant um wel l st r u cture  hav in g a  well lay e r  o f  I nG a N.Also  in s uc h ni tride sem i conducto r l i ght emi tt ing d evice, si n c e the mult ipl e qua n t um well st r uctu r eh as aplural ity
 often_have a_need for above surface_communications. Such_a_need, for_example,_exits when the_submerged vehicle does_not know its exact_location and wishes_to_access the Global Positioning System satellite to obtain a position fix. To establish a_communication_link with_the_satellite_it is necessary for the_submerged vehicle to send an_antenna to_the surface with a link to the submerged_vehicle._This is accomplished_by placing the antenna in a buoy having sufficient_buoyancy to ascend to the surface._These buoys are_relatively_large_and, when stored in_the cramped submerged vehicle, occupy much_needed space.
An alternative to storing the_buoy in the vehicle is to tow_the buoy at the end of_a tether coiled within the_vehicle. As_the tether is uncoiled the_buoy commences its_ascent to_the surface. The_size of the buoy, however, generates_appreciable drag on_the vehicle, seriously effecting its maneuverability.
It_is_an objective of_the_current_invention to_provide a buoy_with_variable buoyancy_which_is sufficiently compact at the submerged_depth_of the vehicle to permit convenient internal_storage, or if towed_to_present little drag on_the vehicle. A nitride semiconductor_has been practically developed as a_material of_highly luminous_blue and pure green LED to fabricate light sources of a_full color LED display, a traffic_signal, and an image_scanner. Those_LED_devices has a_basic_structure comprising_a substrate of sapphire, a buffer layer_made of_GaN, n-contact layer made of GaN_doped with Si, an_active_layer made of a single quantum_well (SQW) structure of InGaN or_made of a multiple quantum_well_(MQW)_structure containing InGaN, a p-cladding_layer made of AlGaN doped with_Mg, and a_p-contact layer made of GaN doped with_Mg,_subsequently formed thereon. Such LED device_has_an excellent characteristics that at the_forward_current_of 20 mA, the light_emission wavelength is 450 nm, the_output is 5 mW, and the external quantum efficiency_is 9.1% in_case of the blue LED,_and_the_light emission wavelength is 520 nm, the output is 3_mW, and_the external quantum_efficiency is 6.3% in case of the green LED.
Such nitride_semiconductor light emitting device adapts a double_hetero-structure with an active layer of a single quantum well or_a multiple quantum well structure having a well_layer of InGaN.
Also in such nitride semiconductor_light emitting device, since_the_multiple quantum well structure has a plurality