Many-body optical gain with piezoelectric effects of wurtzite and zinc-blende GaN AlGaN quantum well lasers

The electronic and the optical properties of (0001)-oriented wurtzite (WZ) GaN/AlGaN quantum-well (QW) lasers with the piezoelectric (PZ) effects taken into account are investigated. These results are compared with those of (001)-oriented zinc-blende (ZB) GaN/AlGaN QW lasers. The self-consistent (SC) model with the PZ effects shows that the many-body optical gain of (0001)-oriented WZ QW lasers is greatly reduced by the PZ field and that WZ QWs have significantly larger threshold carrier densities than ZB QWs. However, when the optical gain is plotted as a function of the radiative current density J(rad), it is found that there is no significant difference between the results of the flat-band (FB) model without the PZ effects and the SC model and between the results for ZB and WZ QWs. These can be explained by the fact that the many-body optical gain and the radiative recombination coefficient B-eff simultaneously decrease with the PZ field and the fact that ZB QWs have larger optical gain and B-eff than WZ QWs, respectively. Also, it is shown that the differential gain of WZ QWs has a large decrease due to a reduction in the matrix elements with the PZ field.