A microwave GaAs field-effect transistor

The characteristies of a GaAs FET which uses a Schottky Barrier for the gate are described. As a result of the high mobility of electrons in GaAs and the small contact geometries attainable, experimental n-channel devices have been fabricated which have a maximum frequency of oscillation of about 3 GHz. The device is an interdigitated structure, fabricated on a 2-3 micron n-type GaAs film. This film is grown from the vapor phase on a semi-insulating GaAs substrate. Ohmic source and drain contacts are obtained by alloying a mixture of Ag, In, and Ge. The gate is evaporated aluminium.