Influence of the Barriers on the Temperature Dependence of Threshold Current in GaAs/AlGaAs Quantum Well Lasers

Abstract

It is commonly observed that GaAs /AlGaAs quantum well lasers have a stronger temperature dependence of threshold current than predicted for a two-dimensional system, and it has been suggested that the barrier regions may be responsible for this behavior. Using window devices, we have observed light emission from the barrier regions of lasers with 25 A wide quantum wells, and while this provides direct evidence for the presence of carriers in the barriers; this radiative current is less than 1 percent of the total current. From measurement of threshold current as a function of temperature on devices grown by molecular beam epitaxy using different A1 cells for the barriers, we have demonstrated the strong influence of nonradiative barrier recombination processes on the threshold current. Further measurements of threshold current as a function of hydrostatic pressure show that recombination from the L and X conduction band minima makes an important contribution to the current. These observations are reproduced by a model calculation of threshold current which includes barrier recombination processes. The temperature dependence of these calculated threshold currents is stronger than that in the absence of barrier recombination and is similar to experimental observations. The calculations show how the temperature dependence of threshold depends upon factors such as cavity length and the number of quantum wells. © 1989 IEEE.