Mechanism of photoluminescence in GaN/Al0.2Ga0.8N superlattices

We present photoluminescence (PL) and time-resolved photoluminescence measu rements in GaN/Al0.2Ga0.8N superlattices grown by metalorganic chemical vap or deposition under the optimal GaN-like growth conditions. We found that t he carrier confinement of our samples is better than most of the previous r eports. The dependence of the PL emission energy and intensity on temperatu re, in the low temperature regime, is consistent with recombination mechani sms involving localized states attributed to a small degree of interface fl uctuations. Picosecond time-resolved photoluminescence spectroscopy has bee n employed to probe the well-width dependence of the lifetime of these supe rlattices. We see that the recombination lifetime increases with the decrea se of well width. This behavior can be interpreted by the fact that the eff ect of localization keeping carriers away from nonradiative pathways can be enhanced by a decrease in the well width. This explanation is consistent w ith the temperature-dependent PL data. (C) 2001 American Institute of Physi cs.