LIGHT-EMISSION AND SURFACE-STATES ANNEALING ON GAAS METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR

The annealing mechanism of surface states in the gallium arsenide meta l semiconductor field-effect transistor (GaAs MESFET) is investigated by measuring the light-emission characteristics and excess gate curren ts generated by hot-carriers, Nonuniform light emission is observed wh en the Schottky junction is reverse biased, and the nonuniformity is i ncreased with temperature. On the other hand, uniform and strong emiss ion is observed under RF operation even when the device is biased with a deep pinch-off condition. The reverse and forward Schottky current caused by RF swing may not be a main emission mechanism under RF opera tion. Light emissions due to impact ionization and thermionic field em ission are observed separately. The light intensity of the thermionic field emission has a weak temperature coefficient, while that of the i mpact ionization has a strong negative temperature coefficient. The de creasing rate of the surface states depends on the intensity and the d istribution of the light emission during the operation.