available as an option starting in fall 1955 for its new line of 1956 Chrysler and Imperial cars which first hit the dealership showroom floors on October 21, 1955. The Sony TR-63, released in 1957, was the first mass-produced transistor radio, leading to the mass-market penetration of transistor radios. The TR-63 went on to sell seven million units worldwide by the mid-1960s. Sony's success with transistor radios led to transistors replacing vacuum tubes as the dominant electronic technology in the late 1950s. The first working silicon transistor was developed at Bell Labs on January 26, 1954, by Morris Tanenbaum. The first production commercial silicon transistor was announced by Texas Instruments in May 1954. This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs. Field effect transistors The basic principle of the field-effect transistor (FET) was first proposed by physicist Julius Edgar Lilienfeld in 1926, when he filed a patent for a device similar to MESFET and in 1928 when he filed a patent for an insulated-gate field-effect transistor. The FET concept was later also theorized by engineer Oskar Heil in the 1930s and by William Shockley in the 1940s. In 1945 JFET was patented by Heinrich Welker. Following Shockley's theoretical treatment on JFET in 1952, a working practical JFET was made in 1953 by George C. Dacey and Ian M. Ross. In 1948 Bardeen patented the progenitor of MOSFET, an insulated-gate FET (IGFET) with an inversion layer. Bardeen's patent as well as the concept of an inversion layer forms the basis of CMOS technology today. MOSFET (MOS transistor) Semiconductor companies initially focused on junction transistors in the early years of the semiconductor industry. The junction transistor was a relatively bulky device that was difficult to mass-produce, which limited it to several specialized applications. Field-effect transistors (FETs) were theorized as potential alternatives to junction transistors, but researchers initially could not get FETs to work properly, largely due to the troublesome surface state barrier that prevented the external electric field from penetrating the material. In the 1950s, engineer Mohamed Atalla investigated the surface properties of silicon semiconductors at Bell Labs, where he proposed a new method of semiconductor device fabrication, coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below, overcoming the surface states that prevented electricity from