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. (c) 2005 WILEY-VCH Verlag GmbH & Co.