Radiative and nonradiative lifetimes in GaInN/GaN multiquantum wells

Abstract

This paper analyzes a simplified rate equation model of localized exciton emission in GaInN. Expressions for temperature dependent photoluminescence (PL) efficiency and decay time are derived and compared with time integrated (TIPL) and time resolved photoluminescence (TRPL) data for a series of multiquantum well light emitting diodes with varying In composition in the active region. Time resolved photoluminescence is measured up to relatively high temperature (540 K) and a decreasing efficiency coupled with a peak energy decay time that is weakly dependent on temperature is observed. The decay time at peak emission energy begins to decrease at a temperature that depends on the In content in the quantum wells. The analysis developed here demonstrates that application of the expressions τr=τpl/η and τnr=τpl/(1−η) is not sufficient to determine radiative and nonradiative lifetimes from TRPL and TIPL data in the GaInN system. (Here τr is the radiative decay time, τnr is the nonradiative decay time, τpl is the measured PL decay time, and η is the measured TIPL intensity normalized to the low temperature intensity.) GaInN with even small amounts of In exhibits highly efficient luminescence due to recombination through localizing centers. As relaxation occurs into both defects and localizing states after initial generation with the above GaInN band gap excitation, the number of carriers arriving at localization centers can change with temperature. This temperature dependent change should be considered when calculating relevant decay times from TRPL and TIPL data. This mechanism is distinct from an increase in the intrinsic radiative decay time obtained by applying conventional analysis to extract radiative and nonradiative lifetimes from TRPL and TIPL data.