Spectroscopic studies of real space indirect symmetric GaAs/AlAs short period superlattices |
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Authors: | R Cingolani K Ploog L Baldassarre M Ferrara M Lugarà C Moro |
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Institution: | (1) Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80, Germany;(2) Dipartimento di Fisica, Università di Bari, Via Amendola 173, I-70125 Bari, Italy |
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Abstract: | The band structure and the optical transitions of symmetric ultra-short period (GaAs)
m
/(AlAs)
n
superlattices (n=m is the number of monolayers) have been studied using different spectroscopic techniques, namely photoacoustic spectroscopy, reflectivity and luminescence, photoluminescence excitation and high excitation intensity time-resolved luminescence. Direct observation of the transition from type I to type II energy band alignment is reported for superlattices whose configuration consists of more than 12 monolayers (i.e. m=n>12). The radiative recombination processes associated with the real space indirect transitions have been investigated as a function of the density of photogenerated electron-hole pairs, revealing an unusual density-dependent behaviour. A tentative interpretation in terms of a condensed electron-hole state at the indirect gap is given, which accounts for the long decay time of the type II luminescence at high excitation rate. |
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Keywords: | 78 65 – b 78 55 – m |
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