The story of Pacific Semiconductors Incorporated (hereafter referred to as 'PSI') and their Power Transistor program is an early example of 1.) the Westward migration of semiconductor technology, eventually contributing to the formation of Silicon Valley, and 2.) the creation of new companies out of old by the acquisition of intellectual property and 'hands-on' expertise gained through the movement of essential personnel from one firm to another. This formula for success was and still is paramount to the advancement of scientific thought and research where the freedom to explore one's own dream and to achieve commercial success (or failure) is a driving force in the world-wide semiconductor industry.
In Southern California the Hughes Aircraft Company started research on transistor and diode development soon after Bell Labs announced the invention of the transistor in 1948. This early commitment to semiconductor development provided the fertile ground for a small group of scientists and engineers to finally leave Hughes Aircraft and begin a new semiconductor venture in 1954 called Pacific Semiconductors, owned by another new start-up firm called the Ramo-Woolridge Corp. (later to become TRW). It wasn't long before PSI was a technological leader in the field of diodes, and were quite profitable early on through their patented process of 'glass-to-metal' sealing. PSI began a slower further expansion into transistor development in the later 1950's. See the Oral History of Sanford Barnes on transistor development at PSI. In 1957 M. A. Clark came to the company and brought with him hands-on experience with the new Bell Labs silicon double-diffusion fabrication process. His additional production experience at BTL in Power Transistors would provide PSI a natural lead-in to that growing market segment. The continued refinement of this new diffusion technology would finally lead PSI into the development of a series of high-frequency "triple-diffused" silicon mesa transistors, from small-signal to medium and high-power types.
In 1958, under the auspices of an Air Force semiconductor contract, PSI began development on a series of high-power and high-frequency diffused silicon Power Transistors unlike anything the industry had seen to date. By 1960 these finalized Air Force devices ranged all the way in power from 10-amp to 100-amps, in standard threaded-stud mounts to water-cooled mounts and working up to a cut-off frequency of 50 Mhz. This while most other manufacturers were dealing in single-digit Mhz power designs. Later in 1960-61 PSI released 10-amp production versions of these devices known as the 'PT900' series.