Light-induced capacitance enhancement and successive carrier escape in InGaN/GaN multiple quantum wells

We observed large enhancement of capacitance with strong voltage sensitivity in InGaN/GaN multiple quantum wells with additional laser illuminations. We have found that the observed negative differential capacitance and its related capacitance peaks in the capacitance-voltage profile are due to the photogenerated charge separation and accumulation at the well/barrier interfaces and its subsequent carrier escape by the applied forward bias. By analyzing temperature dependent photocurrent spectra simultaneously, it is shown that photocarrier separation and strong carrier escape simultaneously occur in an individual quantum well. We can analyze the contribution of a single individual quantum well to the total capacitance of the device, resulting from the nanometer scale carrier separation and accumulation, and clarify the detailed process of accumulation and escape of carriers in the respective quantum wells.