Type II indirect and type I direct recombinations in GaAs/A1As single quantum wells

Abstract

Abstract Single quantum wells (SQWs) of GaAs 3 nm thick between wide A1As confining layers were studied by scanning electron microscope cathodoluminescence (CL) and high resolution transmission electron microscopy (HREM). It was found that the CL emission band changed from a single gaussian owing to the indirect X-Γ recombination for a beam energy of 1 keV to a broad asymmetric band with a peak at a higher photon energy for beam energies of 3 keV or higher. This is ascribed to the excitation of both the indirect and a more intense direct Γ-Γ recombination at higher beam energies. HREM cross-sectional observations showed the SQWs to have a width of 10 ± 3 monolayers. This corresponds closely to the SQW width for the direct-indirect cross-over. The full width at half-maximum of the indirect recombination (53 meV) was as expected for a type II SQW of the observed thickness and roughness.