Theoretical study of small-signal transport and noise in semiconductors at high electric fields

The advancement of semiconductor technology has progressively reduced the space and time scales for electron motion in modern devices to a point where a basic understanding of the related physical effects is mandatory for a realistic analysis or simulation of the electrical behavior of these devices. Here, the effect of a high electric field on the small signal transport and electrical noise in silicon and gallium arsenide is examined, theoretically, based on the displaced Maxwellian solution to the Boltzmann transport equation. A small signal circuit model is developed for silicon. Nyquist's formula for thermal noise is used to study the effect of electric field on noise power and power pectral density, and to relate the small signal transient and frequency response to the velocity autocovariance function. Thermal and intervalley noise power spectral density and microwave mobility in gallium arsenide are calculated for various field strengths. The observed high frequency limit to negative differential resistance and the maximum in the current noise power spectral density versus electric field curve are explained.