Effects of reduced internal electric field in InGaN/pseudo-AlInGaN multi-quantum-well on forward leakage current and photocurrent properties

Abstract

The main focus of this work is to find the effects of the internal electric field on the forward leakage current and photocurrent of an InGaN/pseudo-AlInGaN multi-quantum-well (MQW) grown on sapphire substrate using metalorganic chemical vapor deposition. The temperature dependent current-voltage characteristics of an InGaN MQW with and without an AlInGaN barrier (sample A=GaN barrier, sample B=Al0.043In0.036Ga0.921N barrier, sample C=Al0.043In0.052Ga0.905N) exhibit two linearly dependent divisions with different slopes at low (1.0 <= V <= 1.4) and medium (1.6 <= V <= 2.5) bias regions in the 250-300K range. The temperature-insensitive behavior of the characteristic energy and large ideality factors mean that tunneling is the dominant process in the three samples. Distinct tunneling entities at low and medium biases are observed for samples A and B; however, for sample C, thermionic emission gain dominance in the medium bias range. The peculiar behavior in sample C is attributed to suppressed hole-tunneling currents caused by a low internal electric field. Photocurrent experiments using a xenon lamp demonstrate that sample C exhibit higher photocurrent characteristics and that the enhanced photocurrent is due to a reduced internal electric field. The low internal electric field generates a large amount of photo-excited carriers, which cross the potential of QW effectively compared to the conventional GaN barrier.