Recombination lifetimes in InN films studied by time-resolved excitation-correlation spectroscopy

Recombination dynamics in degenerate InN were investigated by means of time-resolved excitation-correlation spectroscopy. The photoluminescence decay times are determined beyond the spectral response and temporal resolution limits of conventional photon-counting detectors. Spectral and temperature dependence of decay times reveal the effects of hole localizations on the recombination mechanisms. At low temperatures, the radiative lifetime τr is insensitive to temperature and significantly longer than that predicted for the radiative band-to-band recombination, indicative of a transition dominated by the free-to-bound recombination without k conservation. Above a certain temperature determined by the electron concentration, we find τr ∼ T3^/2, as expected for the band-to-band transition when the k -selection rule holds. We determine a lower limit for the bimolecular recombination coefficient B in InN at 300 K as 5.6× 10^-11 cm3 /s.