Optical gain calculation of strained hexagonal and cubic GaN/AlGaN quantum well lasers

Theoretical results for the optical gain of strained hexagonal GaN/AlGaN QW lasers are presented. These results are also compared with those for cubic GaN/AlGaN QW lasers. The band structure is calculated by using the Hamiltonian derived based on the Rashba-Sheka-Pikus 6 × 6 Hamiltonian. The parameters in the Hamiltonian are determined by a comparison with those used in the Hamiltonian derived by the k · p method. The optical gains are calculated as a function of the Al composition in the barrier region. It is found that cubic QW lasers show larger optical gains than hexagonal QW lasers in the investigated range of Al compositions. This is due to the fact that the hexagonal QW lasers have a larger averaged effective mass at the zone center compared to that for the cubic QW lasers.