Influence of the carrier density on the optical gain and refractive index change in InGaN laser structures

Abstract

The carrier-induced refractive index change and the linewidth enhancement factor α are investigated by measuring the optical gain in an InGaN/GaN laser structure. Using the Kramers–Kronig relation we determined the maximum refractive index change to −0.0044 for a carrier density four times as large as the transparency carrier density. Though the change is higher than in conventional III–V structures, its influence on the waveguiding properties of the laser structure is small. The α factor varies between 2.1 and 6.3 in the investigated range of the carrier density and is thus comparable to that known from InGaAs/GaAs quantum well structures. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)