TECHNIQUES FOR EXPERIMENTAL FABRICATION OF A 1WATT, 1-GC GALLIUM ARSENIDE TRANSISTOR.

Gallium arsenide transistors with zinc-diffused base structures were built during this quarter. These transistors were built on both melt-grown and n on n epitaxial gallium arsenide. The common emitter current gain cutoff frequency of the transistors was between 300 and 700 mc. The dc current gain was tipically 7, with many ranging up to 20 and 30. Gallium arsenide transistors were also fabricated from p on n epitaxial material. These devices featured uniformly high values of h sub FE, typically 25. The f sub ts were on the order of 80 mc. Transistors were also made using an evaporated emitter stripe geometry on Zn-diffused GaAs. The high temperature 200 C characteristics of a number of Zn transistors were studied during the quarter. Fifty state-ofthe-art Zn-diffused devices have been placed on life test. Radiotracer studies on zinc diffusion show that the shallow junction depth and low surface concentrations needed for an evaporated stripe structure are obtainable with diffusions from SiO2 films. Tracer work on n-type impurity diffusion in GaAs was continued using S35 as a source impurity for diffusion work through oxide films. Junction capacitance vs applied voltage studies have been made on Zn-diffused diodes to double-check the impurity profiles. Similar measurements were also made on Te diodes. Author