Photocurrent Oscillations in Oxygen-Doped Gallium Arsenide

Abstract

Photocurrent oscillations in boat-grown oxygen-doped-GaAs (dark resistivity from 3.0 to 106 ohm cm) are studied at different temperatures under white-light illumination and at 80°K under monochromatic excitation. Higher-resistivity samples show oscillations 20–50°K below room temperature and the oscillation characteristics (period and amplitude) follow closely the variation in the steady-state photocurrent with temperature. Lower-resistivity samples oscillate only at temperatures \lesssim100°K. The oscillation characteristics of all the samples of different dark resistivity follow the spectral response curves at 80°K. From the experimental observations, an energy diagram is presented to explain the phenomenon of photocurrent oscillations in these crystals. It is concluded that two acceptor levels, respectively 0.22 eV and 1.3 eV below the conduction band, are responsible for this phenomenon. The 1.3 eV level is found to be responsible both for the photoconduction and field-dependent trapping of the photoexcited electrons.