Photoluminescence study of carrier localization and recombination in nearly strain-balanced non-polar m-plane InGaN/AlGaN superlattices*

The carrier recombination and localization in near strain-balanced InGaN/AlGaN superlattices grown by plasma-assisted molecular-beam epitaxy was investigated by photoluminescence (PL) spectroscopy. Time-resolved PL shows a recombination lifetime of ~0.3ns, much shorter than that in conventional polar c-plane InGaN/(Al)GaN quantum wells. The temperature dependence of PL energies is not monotonic and experimental PL peak energies are lower than inter-band transition energies calculated using structural parameters obtained from high-resolution x-ray diffraction. This indicates the existence of In composition fluctuation. Sites with high In composition act as localization centers. Time-resolved PL in magnetic field indicates that radiative recombination mainly takes place in localization centers. The localization depth is found to be ~13meV, which is much lower than previously reported for m-plane InGaN/GaN quantum wells. Shallow localization potential contributes to narrower transition peak, but reduces the isolation from non-radiative recombination centers. Rapid drop of PL intensity as temperature increases indicates strong non-radiative recombination at room temperature.