A Photo-Initiated Self-Sustaining Conduction State in Semi-Insulating GaAs

High power switching using GaAs:Cr and undoped GaAs initiated by 1.06 micrometer YAG laser and 0.5 micrometer DYE laser at liquid nitrogen temperature was demonstrated. Some unusual properties of photoconductivity, such as the negative differential motility and the change of the relaxation time of the induced carriers due to the different intensity of light injection, have been investigated. For field strength above 20 kv/cm a self-sustaining conduction state was observed, following the photoconductive current pulse with a delay of 1-UOO ns. Various features of this second signal are presented. In order to understand the mechanism responsible for the self-sustaining conduction state, a heating model was investigated analytically and found to be inadequate. Possible mechanisms are discussed.