Exciton localization in Al‐rich AlGaN ternary alloy epitaxial layers

Exciton localization in Al-rich AlGaN ternary alloy epitaxial layers has been studied by means of temperature-dependent photoluminescence (PL) spectroscopy. Anomalous temperature dependence of the PL peak energy (red-blue shift) was observed, which enabled us to estimate the localization energy of excitons. The localization energy increased as the 1.2th power of the exciton linewidth. The value of exponent for Al-rich alloys was smaller than that for Ga-rich alloys. This indicated that the excitons in Al-rich alloys were strongly localized compared to that in Ga-rich alloys. In addition, the exponent value for Al-rich alloys increased with increasing excitation power density. This increase in the exponent suggested that the exciton population approached the extended states owing to the saturation of localized states by photo-generated excess excitons. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)