Influence of space charges on the resonant photoconductor employing a moving laser induced grating

Abstract

We discuss the performance of a recently proposed semiconductor device that converts the optical signal of frequency modulated laser beams into electrical signals of the same frequency in the GHz range. The device relies on a synchronous drift of photogenerated electrons with a moving intensity grating obtained from the interference of frequency shifted coherent lasers. The linearized rate equations for electrons and holes are solved in the limit of weak contrast of the intensity grating taking both drift and diffusion terms into account. One drift term due to the externally applied electric field is responsible for a resonantly enhanced amplitude of the photoelectron grating. A second drift term is related to internal fields set up by internal space charges and effectively reduces the electron grating amplitude in the lifetime regime.