Surface-barrier transistor

The surface-barrier transistor is a type of transistor developed by Philco in 1953 as an improvement to the alloy-junction transistor and the earlier point-contact transistor. Like the modern Schottky transistor, it offered much higher speed than earlier transistors and used metal–semiconductor junctions (instead of semiconductor–semiconductor junctions), but unlike the schottky transistor, both junctions were metal–semiconductor junctions.

Philco used a patented process of applying two tiny electrochemical jet streams of liquid indium sulfate (electrolyte solution) on opposite sides of a thin strip of N-type germanium base material. This process would etch away and form circular well depressions on each side of the N-type germanium base material, until the germanium base material was ultra thin and having a thickness of approximately a few ten-thousandths of an inch. After the etching process was finished, the polarity applied to the electrolyte was reversed, resulting in metallic indium being electroplated into these etched circular well depressions, forming the transistor's emitter and collector electrodes. The Philco surface-barrier transistor was the world's first high-frequency transistor was developed and produced at the Lansdale Tube Company-division of Philco Corporation, which was capable of obtaining frequencies up to 60 MHz.

The world's first all-transistor car radio, was developed and produced by Chrysler and Philco in 1955. Chrysler offered this all-transistor car radio, Mopar model 914HR, available as an "option" in the fall of 1955, for its new line of 1956 Chrysler and Imperial cars. Philco was the manufacturer of these all-transistor car radios for the Chrysler Corporation and had also used its surface-barrier transistors in the radio's circuitry design.

Starting in 1955, Philco had decided to sell commercial manufacturing license agreements with other large electronic semiconductor companies, which allowed them the right to produce and sell its high-frequency surface-barrier transistors. Sprague Electric Company was one of the first companies to purchase a license agreement from Philco in late 1955 and started to manufacture the surface-barrier transistors under its Sprague name, in early 1956. Another company to purchase a license agreement from Philco in early 1957, was Semiconductors Limited, a division of the British-based Plessey Company. In 1959, General Transistor Corporation had also purchased a license agreement from Philco, to manufacture its complete line of high-speed transistors.

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