Carrier dynamics with blue emission in asymmetrically coupled QaN/Al _0.5Ga_0.5N/GaN multiquantum wells

Coupled multiquantum well structures consisting of GaN(10 Å)/Al _0.5Ga_0.5N(22 Å)/GaN(20 Å) bounded by Al _0.5Ga_0.5N (100 Å) barriers were characterized by photoluminescence measurements. The recombination dynamics of carriers localized in asymmetric double quantum wells were studied by analyzing temperature-dependent and time-resolved photoluminescence spectra. The authors observed carrier transfer between weakly and strongly localized states which resulted in a stronger blue emission with increasing temperature, and they analyzed its effects on the spectra in terms of the quantum confined screening effect. Time-resolved measurements yielded lifetimes of various transitions which had different origins ranging between ∼120 and ∼1300 ns.