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Producing PNP Type GaAs Transistors Having Extremely Thin Bases

IP.com Disclosure Number: IPCOM000094162D
Original Publication Date: 1966-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gansauge, P: AUTHOR [+2]

Abstract

The production of PNP type GaAs transistors with a current gain of greater than 1 requires extremely thin bases which must not exceed 0.2 microns. This is because the carriers have only a very short life in the base.

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Producing PNP Type GaAs Transistors Having Extremely Thin Bases

The production of PNP type GaAs transistors with a current gain of greater than 1 requires extremely thin bases which must not exceed 0.2 microns. This is because the carriers have only a very short life in the base.

Such a small base thickness can be achieved by diffusion only if the diffusion fronts are extremely plane over the entire surface of the transistor. This requires that the surfaces subjected to the diffusion processes do not corrode. Corrosion can be prevented by the following process steps:

1) For the base diffusion process using tin, the surface of the GaAs wafer is first covered with a thin SiO(2) layer. The latter protects the surface from corrosion while it does not prevent the diffusion of the tin in to it.

2) For the emitter diffusion, the diffusion ampoule together with its contents, GaAs wafer and zinc arsenide as the diffusion source, are baked out at 300 degrees C for 30 minutes during the evacuation. This allows impurities which are the main causes of surface corrosion to evaporate.

This method can be employed also in a corresponding manner on other semiconductor materials with unstable surfaces.

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