Polar optical phonon instability and intervalley transfer in III-V semiconductors

Following a course of analysis similar to that employed by Callen in his tr eatment of electric breakdown in ionic crystals, we develop a simple, one-d imensional, analytical model, which describes electron transport in III-V s emiconductors with a nondegenerate conduction band minimum. We focus on the polar optical phonon scattering mechanism, as this is the dominant energy loss mechanism in these materials. Equating the power gained from the field with that lost through polar optical phonon scattering, we demonstrate tha t beyond a certain critical electric field, dependent on the material and o n the temperature, that the power gained from the field exceeds that lost d ue to scattering. The instability which results leads to a dramatic increas e in the electron energy and is responsible for the onset of intervalley tr ansitions. Applying this model to the specific cases of gallium arsenide an d wurtzite gallium nitride, we find that the 300 K critical fields in these materials are 2.42 and 114 kV/cm, respectively. The predictions of our ana lytical model are compared with those of Monte Carlo simulation and are fou nd to be in satisfactory agreement. (C) 2001 Published by Elsevier Science Ltd.