Thermal and spectral dependence of low-frequency oscillations in semi-insulating GaAs:In

We have investigated the thermal dependence of low-frequency current oscillations in the range of 140–400 K for semi-insulating (SI) GaAs resistor structures illuminated with sub-band-gap light. We have also investigated the spectral dependence of the low-frequency current oscillations in SI GaAs for illumination in the range of 0.85–1.25 μm. We find that the oscillation frequency is proportional to the carrier concentration. The thermal and the spectral measurement results both support the hypothesis that the low-frequency oscillations are caused by carriers interacting with the EL2 level and that the presence of holes can significantly alter the oscillation frequency. The behavior of the oscillations can be qualitatively described by a simple empirical expression with the assumption that EL2 exhibits field-enhanced capture from the Γ valley, although the exact behavior of the enhanced capture is not fully understood.