Observation of ultra-low frequency photocurrent self-oscillation in InxGa1-xAs quantum wells

Photocurrent (PC) response properties have been investigated of In_xGa_1-xAs/Al_0.15Ga_0.85As quantum wells (QWs) embedded in an intrinsic region of a p-i-n diode as a function of temperature and bias voltage. It is found that the PC signal intensity shows self-oscillations with a characteristic frequency of about 0.1 Hz at low temperatures below 60 K under the reverse bias conditions by illumination at wavelengths near the leading n = 1 heavy-hole exciton resonance. The frequency of the self-oscillation depends on the illumination power. The self-oscillations are only observed for QWs with higher In fractions (with x = 0.10 and 0.15) with delayed PC rises. These results suggest that the low-frequency PC self-oscillation is caused by oscillating electric fields due to photogenerated charge carriers trapped at deep localized centers within the In_xGa_1-xAs QW regions.