Carrier dynamics in wide-band-gap AlGaN/AlGaN quantum wells

Abstract

Carrier dynamics in a set of AlGaN/AlGaN multiple quantum wells (MQWs) has been investigated. High-Al-content MQWs with well widths varying from 1.65 to 5.0 nm and fixed barrier width were grown by metal-organic chemical vapor deposition. Time-resolved photoluminescence (PL) and light-induced transient grating technique were used to study transient processes in the samples. An observed increase in carrier lifetime with decreasing well width was explained by stronger carrier localization due to the well thickness fluctuations, which prevent the migration of carriers to nonradiative recombination centers. The initial PL decay was shown to be influenced by the screening of the built-in electric field, which spatially separates electrons and holes. The influence of screening on the PL decay becomes stronger in broader quantum wells and with increasing excitation power density up to the saturation caused by the complete screening of the built-in electric field. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.