Optical spectroscopy of InGaN epilayers in the low indium composition regime

Photoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the law indium(In) composition regime. Room temperatur e PL showed a factor of 25 increase in integrated intensity as the In compo sition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for ther mal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In (x=0 .07) showed a strong spectral variation in decay time across the T=4K PL re sonance, indicative of recombination from localized states at low temperatu res. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate tha t non-radiative recombination is less effective with increasing in composit ion.