Observation of ultra-low frequency photocurrent self-oscillation in In/sub x/Ga/sub 1-x/As quantum wells

Photocurrent (PC) response properties have been investigated of In/sub x/Ga/sub 1-x/As/Al/sub 0.15/Ga/sub 0.85/As 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/sub x/Ga/sub 1-x/As QW regions.