INTERFACE LUMINESCENCE OF GAAS/GA1-XALX AS HETEROSTRUCTURES - THRESHOLD EFFECT OF THE INTERFACE FORMATION CONDITIONS

Photoluminescence of single GaAs/Ga1-xAlxAs heterostructures was studied as a function of the interface formation conditions (epitaxy temperature, layer growth rate, etc.). Photoluminescence spectra contained, apart from the bulk luminescence bands of GaAs and Ga1-xAlxAs, a band related to the interface (interface luminescence band). It has been shown that the emergence of interface luminescence critically depends on the interface formation temperature TF: it can be observed for temperatures above TcrF and vanishes below this threshold. This temperature threshold decreases with decreasing value of the layer growth rate and initial supersaturation and depends on perfection and/or doping of the heterostructure narrow-gap region (GaAs). This sharp, threshold-type emergence and disappearance of the interface luminescence has been accounted for by invoking two models. The first model is that of the interface luminescence as due to annihilation of the heterodimensional interface exciton formed by a two-dimensional (2D) electron (hole) at the interface and a 3D hole (electron) in the bulk of GaAs; the second model assumes that the roughening phase transition at the substrate surface produces a drastic change in the interface morphology (at the microscopic level) causing a sharp change in conditions required for the existence of the heterodimensional interface exciton. © 1995 The American Physical Society.