Consistency on Two Kinds of Localized Centers Examined from Temperature-Dependent and Time-Resolved Photoluminescence in InGaN/GaN Multiple Quantum Wells

Due to structural imperfection and indium content fluctuation, carriers’ localization in an InGaN-based active layer can produce efficient luminescence and unusual thermodynamic behaviors. Spectral features associated with localization, such as the “S-shaped” shift of peak energy in temperature-dependent photoluminescence (PL) and the nonexponential decay in time-resolved photoluminescence (TRPL), have not yet formed a comprehensive physical interpretation. In this work, the thermal evolution of carriers’ decay process is examined by spectroscopic approaches in high-efficiency InGaN/GaN multiple quantum well (MQW) samples. Based on the localized-state ensemble model, the peak shift in temperature-dependent PL is excellently fitted by the “red” and “blue” localization centers, which perfectly match with the fast and slow processes resolved from TRPL using biexponential model. All variations in emission peak, line shape, filling position, and lifetime with temperature are elucidated by carriers redistributing between two kinds of localization centers according to the density of states. Meanwhile, the impact of substrate and underlying layers in MQW samples has also been compared. Through such systematic analysis, the dynamics of carriers in MQWs have been quantitatively discussed, and a comprehensive understanding on the localization-induced luminescence mechanism is achieved.