Optical gain and spontaneous emission of strain-compensated InGaN-AlGaN quantum wells including carrier screening effect

Abstract

Strain-compensated InGaN quantum well (QW) active region employing tensile AlGaN barriers was analyzed as improved gain media for laser diodes emitting at 430-440 nm by taking into account the carrier screening effect. The use of strain-compensated InGaN-AlGaN structure is advantageous because the tensile barriers compensate the compressive strain in the InGaN QW and the larger band offset allows high temperature operation. The band structure is calculated by using a 6-band <i>k times p </i>formalism, taking into account valence band mixing, strain effect, spontaneous and piezoelectric polarizations. The carrier screening effect is incorporated in the calculation, which is solved self-consistently. The spontaneous emission spectra show a significant improvement of the radiative emission for strain-compensated structure. The optical gain analysis shows enhancement in the peak optical gain for the strain-compensated QW structures. Threshold analysis of both the conventional InGaN-GaN QW and strain-compensated InGaN-AlGaN QW active regions indicate a reduction in the threshold carrier density and threshold current density for diode laser employing the strain-compensated QW as its active region.