THERMALLY DETECTED OPTICAL-ABSORPTION AND PHOTOLUMINESCENCE IN A GAAS/GAALAS MULTIQUANTUM-WELL SAMPLE

A multiquantum well (MQW) GaAs/GaAlAs system is studied by a non-conventional technique of thermally detected optical absorption (TD-OA) in which the sample temperature variation is measured by a germanium thermometer at 0.5 K. In such a sample, for which the holder and quantum well materials are the same, the QW transitions give rise to temperature minima. The latter are interpreted in terms of intensity variations of the energy reflected at the interfaces of the wells close to the excitonic recombinations. The TD-OA spectra corresponding to the n = 1 heavy-hole and light-hole excitonic transitions in the wells are examined, together with the spectra obtained by conventional photoluminescence. Doublet lines involving QW excited levels, a component of which is due to a transition only allowed by valence band mixing, are also detected as in photoluminescence excitation.