Dimensionality of excitons in laser-diode structures composed of InxGa1-xNmultiple quantum wells

Temperature dependence of radiative and nonradiative lifetimes of localized excitons has been assessed in the laser diode structures composed of In0.2 0Ga0.80N (6 nm)/In0.05Ga0.95N (6 nm) multiple quantum well (MQW) [sample (a )] and In0.10Ga0.90N (3 mm)/In0.02Ga0.98N (6 nm) MQW [sample (b)] by means of time-resolved photoluminescence spectroscopy. The radiative lifetimes (t au(rad)) in sample (a) were almost constant around 6 ns between 23 K and 20 0 K, suggesting the mesoscopic effect where excitons are confined in the ze ro-dimensional potential such as a quantum-dot-like region. This interpreta tion fairly agrees with the result that the emission was ascribed to the lo calized excitons whose depth is about 250 meV. The tau(rad) value in sample (b) was 460 ps at 20 K and grew with increasing temperature. It was found that the depth of exciton localization in sample (b) is so weak that excito ns reveal a nearly two-dimensional feature at RT as a result of the delocal ization effect. [S0163-1829(99)08815-3].