Origin of multiple peak photoluminescence in InGaN/GaN multiple quantum wells

Optical spectroscopy has been performed for a set of In0.12Ga0.88N/GaN mult iple quantum wells (MQW) grown by metalorganic vapor phase epitaxy at 820 d egrees C. Time-resolved, temperature- and power-dependent photoluminescence as well as spatially-resolved cathodoluminescence measurements have been a pplied to elucidate the nature of the recombination mechanisms responsible for the radiative transitions in the samples. The photoluminescence spectra in this set of samples are dominated by strong multiple peak emissions ass ociating with both confined levels of the MQW system (the higher energy ban d) and with strongly localized states of energies much lower than the QW ba nd gap. We suggest that the photoluminescence originate from (i) the MQW ex citon recombination, (ii) excitons localized in the quasidot regions with i ndium concentrations higher than in the alloy due to segregation processes, and (iii) from localized states in zero-dimensional quantum islands create d by surface defects such as pits and V defects. Buried side-wall quantum w ells caused by V defects might also influence the photoluminescence spectra . (C) 2000 American Institute of Physics. [S0021-8979(00)00117-1].