A comparison of the optical characteristics of AlGaN, GaN, and InGaN thin films

Abstract

We have investigated the optical properties of InGaN, GaN, and AlGaN epilayers using photoluminescence (PL), PL excitation, time-resolved FL, and optically pumped stimulated emission (SE) spectroscopy. The InGaN layers had a larger (i) Stokes shift, (ii) spectral broadening, (iii) decay time, and (iv) PL redshift with time than AlGaN layers of comparable alloy composition. The optically pumped SE behavior of InGaN layers is significantly different than that of GaN and AlGaN layers. This is attributed to the suppression of nonradiative recombination and the elimination of below-gap induced absorption in highly excited InGaN alloys, effects that accompany the incorporation of indium into GaN. In contrast, the SE behavior of AlGaN layers is similar to that of highly excited GaN.