Band-structure engineering of a cubic GaN quantum-well laser

A theoretical model of a cubic GaN quantum-well laser is studied taking into account the effects of strong spinorbit (SO) split-off band coupling on the valence-band structure and the optical gain within the 6 × 6 Luttinger-Kohn model. It is expected that a very narrow separation (10 meV) between the SO band and the heavy- and light-hole bands causes two undesirable effects on the lasing of GaN quantum well: 1) the TE and the TM polarizations have comparable magnitudes over the wide range of carrier densities and 2) the SO band will be easily occupied by the injected holes which in turn reduces the injection efficiency or increases the lasing threshold. A combination of strain and the use of alloy is proposed to reduce the hole and the electron masses and to increase the SO band separation in order to reduce the lasing threshold.