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

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