PHOTOREFRACTIVE EFFECT IN GAAS AT LOW-TEMPERATURE - INFLUENCE OF THE METASTABLE STATE OF THE EL2 DEFECT

Abstract

We present here a theoretical and experimental analysis of photorefractive two-beam coupling in undoped GaAs as a function of temperature. Three major features are experimentally observed, firstly, a change of sign of the photorefractive beam coupling gain around 150 K, secondly, an enhancement of the space charge field by a factor 2 compared to the diffusion field and, finally, a strong peak of the absorption grating amplitude around 150 K. A photorefractive model is established that includes the metastable state of the EL2 defect with its optical properties (optical generation and optical recovery). It predicts all observed features correctly and is in good agreement with the experimental data.