Unveiling asymmetric carrier dynamics and space-charge compensation in InGaN/GaN multiple quantum wells via capacitance transient spectroscopy

Abstract

Carrier dynamics, particularly the transition between localized and delocalized states within quantum wells (QWs), are fundamental to the performance of InGaN/GaN optoelectronic devices. In this work, an anomalous capacitance transient phenomenon was observed using a custom-designed photoelectric synergetic transient spectroscopy system. We demonstrate that the thermal activation process of multiple QWs is fundamentally distinct from classical point-defect signatures. Due to polarization-induced asymmetric potential barriers, thermally emitted carriers from 2D ground states to 3D continuum states are not fully released as free charges but remain localized near the space-charge region. These localized carriers act as dynamic compensation centers, triggering a macroscopic redistribution of the space charge to re-establish electrostatic equilibrium. By varying bias conditions, we distinguish the non-equilibrium dynamics of depletion region expansion and contraction. This study provides a new framework for characterizing carrier transport and spatial charge redistribution, offering a definitive clarification of the non-equilibrium physics in nitride-based quantum structures.