INTERFACE LUMINESCENCE OF GAAS GAALAS STRUCTURES - RELATIONSHIP WITH HETEROJUNCTION FORMATION CONDITIONS/

The photoluminescence of single GaAs/GaAlAs heterostructures was studi ed as a function of the heterojunction formation conditions: the epita xy temperature, the donor concentration in GaAs, and the crystallizati on driving force. In addition to bands of the bulk luminescence of GaA s and GaAlAs, the photoluminescence spectra contain a band due to the heterojunction (a band of interface luminescence). There is a threshol d value of the heterojunction formation temperature for the existence of this interface luminescence. Specifically, the interface luminescen ce arises if the temperature is above T(cr)F, while it disappears belo w this temperature. The threshold temperature T(cr)F decreases with de creasing crystallization driving force during the formation of the het erojunction. It depends on the structural quality of the narrow-gap re gion (GaAs) of the heterostructure. The threshold for the onset and di sappearance of the interface luminescence is explained on the basis of two assumptions. First, it is assumed that the interface luminescence is due to the annihilation of an interface exciton formed by a 2D ele ctron at the heterojunction and a 3D hole. Second, it is assumed that a change in the heterojunction formation mechanism upon a roughening p hase transition at the substrate surface leads to an abrupt decrease i n the number of inhomogeneities in the plane of the heterojunction. Th e effect is to promote the formation of interface excitons.