Optical Quenching of Photocurrent Oscillations in Cr-Doped GaAs

Abstract

Low frequency photocurrent oscillations in compensated semi-insulating GaAs(1, 2) and in CdS (3, 4) crystals have been reported by a number of authors. Occurring in a region of negative differential resistivity, these oscillations with amplitude and frequency varying as a function of temperature, applied electric field and carrier concentration are generally attributed to travelling high field domains induced by either field quenching (3) o r field dependent trapping (5) at some impurity level in the material.We wish to report here on the infra-red quenching of such oscillations in Crdoped GaAs in relation with some slow effects in the low field photoconductivity of the same material. The measurements were made at 90 K on monocrystalline samples having a room temperature dark resistivity in excess of 2x10 Q cm. Two infra-red monochromators were available, one for excitation and one for quenching. 0 8 0