Theoretical analysis of the threshold current density in GaN/AlGaN strained quantum well lasers with a modulation-doped structure

The dependence of the threshold current density on the doping type and dopant concentration in GaN/AlGaN modulation-doped (MD) strained quantum well (QW) lasers is theoretically investigated. This investigation is based on a detailed band structure calculation using the tight-binding method. It is found that the threshold current density of GaN/AlGaN n-type MD-QW lasers can be reduced to 1/2-1/3 that of undoped lasers due to the reduced transparent injected carrier density. The threshold current in p-type MD lasers, however, increases because of decreased carrier lifetime. These results show that n-type MD-QW lasers are more suitable for short-wavelength lasers based on III-V nitrides.