Threshold behavior of (GaAl)As-GaAs lasers at low temperatures

Abstract

The temperature dependence of the threshold current, differential quantum efficiency, and internal loss have been measured in the temperature range 10–293 °K. The threshold current increases relatively slowly with temperature above 100 °K and is independent of the impurity concentration. Theoretical calculation shows that this behavior is to be expected for a band-to-band transition that follows k selection. The threshold behavior at low temperatures (? 80 °K) depends strongly on the type and concentration of the impurity. The relatively fast decrease in threshold below 100 °K shows saturation for an active layer with n-type impurities or with high-concentration p-type impurities. The saturation is attributed to the carrier diffusion length becoming smaller than the active-layer thickness. The internal differential quantum efficiency is near unity and is independent of temperature. The internal loss, however, decreases with temperature due to reduction in free-carrier absorption.