Electroluminescence observation of nanoscale phase separation in quaternary AlInGaN light-emitting diodes

摘要

Anomalous temperature-dependent electroluminescence (EL) of Al_(0.06)In_(0.02)Ga_(0.92)N/Al_(0.1)Ga_(0.9)N multiple-quantum-well light-emitting diodes was investigated. At low temperatures and low currents, the EL was dominated by narrow peaks arising from GaN band edge (3.47 eV) and AlGaN localized state emission (3.59 eV). At 150 K, as thermalized carriers surmounted a static nanobarrier surrounding In-rich nanoclusters, the EL shifted to low-energy emission at 3.39 eV. These EL anomalies are evidence that, contradictory to theoretical predictions, there remains a strong effect of compositional fluctuation toward nanoscale phase separation in low In/Al AlInGaN alloys. During the interphase transfer at 150 K, the majority of excitons underwent nonradiative decay, leading to a sharp decrease in quantum efficiency by over one order of magnitude.