Optical gain in wurtzite ZnO/ZnMgO quantum well lasers

The optical gain of wurtzite ZnO/ZnMgO quantum well (QW) lasers is investigated using the non-Markovian gain model with many-body effects. The results are compared with those of GaN/AlGaN QW lasers. The ZnO/ZnMgO QW lasers are found to have a much larger optical gain than the GaN/AlGaN QW lasers for a given sheet carrier density. This is mainly attributed to the fact that the average hole effective mass and the transition matrix element of ZnO/ZnMgO QW lasers are smaller and larger than those of GaN/AlGaN QW lasers, respectively. Also, the radiative current density contribution to the threshold current density of ZnO/ZnMgO QW lasers is expected to be markedly reduced compared with that of the GaN/AlGaN QW lasers if a large threshold carrier density (> 3 × 10¹⁹ cm^-3) is required for both systems. These results show that ZnO-based QW lasers are promising candidates for optoelectric applications in visible and UV regions.