Understanding the degradation mechanisms of InGaN/GaN multiple quantum well UV photodetectors submitted to different current stresses.

Abstract

The degradation characteristics of InGaN/GaN multiple quantum well (MQW) photodetectors (PDs) stressed at 100 and 200 mA over 480 h are investigated. We have observed that the luminescence intensity, short circuit current density, and open circuit voltage decrease strongly, whereas the leakage current increases intensely due to the constant current stress. The strong activity of the Mg dopant and trap-assisted tunneling under the direct current stress are critical factors in the degradation of InGaN/GaN MQW PDs. Further, the photocurrent spectroscopy results reveal that for 100 mA stress current, the peak value of relative external quantum efficiency (EQE) slightly increases due to the widening of the space-charge region while, for the 200 mA of stress current, the peak value of EQE decreases (∼15.4%) due to some permanent damages in the active region and/or the metal/semiconductor interface, and the associated resistive effects.