Observation of excitons formed by the holes confined at the Al0.5Ga0.5As/GaAs interface

The radiative recombination in the Be-doped single heterojunction Al0.5Ga0. 5As/GaAs, so-called H-band, has been studied by photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy. Magnetophotoluminescence m easurements were also performed. The H-band was interpreted as the recombin ation of holes confined on the ground level in the quantum well at the inte rface and electrons from GaAs conduction band. The carriers involved in the recombination originate from 3D excitons excited in the flat band region o f GaAs, which diffuse towards the interface. In the PLE spectra two new lin es were observed. We interpret them in means of short life-time excitons co mposed of a confined 2D hole and a free electron, which are excited near th e interface. (C) 2000 Elsevier Science B.V. All rights reserved.