New photoluminescence effects of carrier confinement at an AlGaAs/GaAs heterojunction interface

Abstract

An unusual new line has been observed in the low-temperature photoluminescence spectrum of GaAs/AlGaAs epilayers grown by liquid-phase epitaxy, which represents a unique probe of the heterointerface. A very strong, broad and asymmetric line is seen, with peak energy ranging from that of the bound exciton to that of the shallowest acceptor, increasing roughly linearly with the logarithm of the excitation power. The intensity is seen to exhibit a very strong temperature dependence as the temperature is varied from 1.4 K up to about 20 K where the line falls below the background luminescence intensity. Intensity and energy dependence of the luminescence as a function of the Al mole fraction on one side of the junction is also investigated. By employing a novel step-etching technique, this transition is shown to originate from the GaAs/AlGaAs heterojunction. A qualitative model is proposed to explain the observed data.