Techniques For Experimental Fabrication Of A 1 Watt 1gc Gallium Arsenide Transistor

Techniques for Experimental Fabrication of a 1-watt, 1gc Gallium Arsenide Transistor

Fabrication technologies needed to achieve n-p-n GaAs transistor performance, such as emitter formation and base diffusion, were investigated. Initially, Mg-Mn was used to produce p-type base layers, and a Sn pellet was used to form an alloyed emitter. Adding small amounts of In to the Sn improved device performance. To make a stripe geometry transistor, one adaptable to widely varying geometries, several combination of Sn, Ge, Au, and Al were investigated as emitter materials. One, Sn-Al(2%), was used almost exclusively in the standard transistor process. Both two-stripe and three-stripe GaAs transistors were made during the period of this contract, using Mg-Mn diffused based layers that had been reduced in thickness by an etching procedure. A method of diffusing Zn into GaAs to produce uniform base layers reproducibly was developed using techniques for sputtering both SiO2 and Zn. To determine the importance of various process parameters, theoretical studies were made of various device structures to predict their characteristics. Intensive studies were also made of the electro-optical properties of the GaAs used in this program in an attempt to determine material characteristics, such as diffusion lengths and impurity levels, that could be related to transistor performance.

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