Analysis of the temperature and excitation intensity dependencies of photoluminescence in undoped GaN films

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Steady-state photoluminescence (PL) from undoped wurtzite GaN has been studied in detail over a wide range of temperatures and excitation intensities. Both the observed steps in the temperature dependence of the PL intensity, and the nonlinear dependence of the PL intensity on excitation power for different PL bands are quantitatively explained by competition between different recombination channels. Hole-capture cross sections, defect concentrations, and thermal activation energies of the main acceptors in undoped GaN are estimated from the analysis of temperature and excitation intensity dependencies of the PL.