Intensity dependent time‐resolved photoluminescence studies of GaN/AlGaN multiple quantum wells of varying well width on laterally overgrown a ‐plane and planar c ‐plane GaN

GaN/AlGaN multiple quantum wells (MQWs) of varying well width grown on planar c ‐plane GaN and a ‐plane GaN templates fabricated by lateral epitaxial overgrowth (LEO) have been studied by subpicosecond photoluminescence (PL) downconversion and time‐correlated single photon counting as a function of pump intensity. Although slower room temperature decays at higher carrier density are observed in both a ‐plane LEO and c ‐plane MQWs with 3 nm well width, this behavior is attributed to suppression of electric field‐enhanced recombination through the barriers and interfaces at higher carrier density in the c ‐plane MQW, while in the a ‐plane LEO MQW the sublinear dependence of the PL signal at t = 0 on pump intensity implies that the radiative lifetime in this high quality sample increases due to a reduction in excitonic oscillator strength associated with phase space filling. The combination of more intense time‐integrated PL spectra and shorter PL lifetimes with decreasing well width in the a ‐plane LEO MQWs for low pump intensity suggests that the radiative lifetime becomes shorter due to the accompanying increase in exciton binding energy and oscillator strength at smaller well width. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)