Structural dependencies of many-body optical gain with piezoelectric field effects in wurtzite GaN/AlGaN quantum well lasers

摘要

Abstract: The many-body optical gain with piezoelectric field effects in wurtzite GaN/Al$-x$/Ga$-1-x$/N quantum-well lasers is investigated as a function of compressive strain and well thickness. Our self-consistent (SC) model, which solves self- consistently the band structure with the piezoelectric field, shows that the peak gain gradually decreases with increasing compressive strain at a fixed carrier density. On the other hand, a flat-band (FB) model ignoring the piezoelectric field shows an increase of the peak gain with compressive strain. This means that quantum-well (QW) lasers with a larger strain does not improve the laser gain due to the large strain- induced piezoelectric field in the well and it is important to use the self-consistent model to account for the piezoelectric field effects. For a fixed strain in the well using an aluminum mole fraction x equals 0.2 in the barriers, our models show that, at a given carrier density, optical gain increases with well thickness until 3.5 nm, then remains almost constant. It indicates an optimum well width for optical gain. !19