Optical transitions and gain in group-III nitride quantum wells

The convenient basis representation for the valence band Hamiltonian in wur tzite semiconductors is proposed and the polarization selection rules in Ga N-based quantum wells are found. The polarization dependent optical matrix elements in quantum wells are calculated for a finite in-plane electron mom entum, that allows to calculate peak optical gain and laser threshold in th e GaN-based quantum well structures. This article also addresses the role o f alloy inhomogeneities in the optical gain in quantum well lasers. The pea k gain is found as a function of statistical broadening caused by the In-co ntent fluctuations. It is shown that the composition fluctuations in the ac tive region influence the gain differently depending on a light polarizatio n. The absolute value of the calculated gain is found to be in agreement wi th the experiment. (C) 2000 American Institute of Physics. [S0021-8979(00)0 6223-X].