THEORY OF DRIFT CURRENT INSTABILITIES IN N-TYPE GAAS TAKING INTO ACCOUNT THE ELECTRON THERMAL PRESSURE-GRADIENT

A theoretical investigation has been made of the effect of the electron thermal pressure gradient on the interaction of surface optical phonons and surface space-charge waves in n-type GaAs in which a drift current is flowing parallel to the surface. The range of frequency for which amplification of the slow surface space-charge wave occurs has been calculated in the nonretarded limit as a function of the ratio of the thermal pressure gradient coefficient-beta to the drift velocity V0. For values of beta/V0 greater than approximately 0.15, the frequency range for amplification decreases with increasing beta/V0, reaching zero when the latter quantity reaches unity.