Thermal expansion contribution to the temperature dependence of excitonic transitions in GaAs and AlGaAs

AUTOR(ES)

Loureno, S. A., Dias, I. F. L., Duarte, J. L., Laureto, E., Poças, L. C., Toginho Filho, D. O., Leite, J. R.

FONTE

Brazilian Journal of Physics

DATA DE PUBLICAÇÃO

2004-06

RESUMO

Photoluminescence and photoreflectance measurements have been used to determine excitonic transitions in the ternary Al xGa1-xAs alloy in the temperature range from 2 to 300 K. The effect of the thermal expansion contribution on the temperature dependence of excitonic transitions for different aluminum concentrations in the Al xGa1-xAs alloy is presented. Results from this study have shown that the negative thermal expansion (NTE) in the Al xGa1-xAs alloy, in the low temperature interval, induces a small blueshift in the optical transition energy. In the temperature range from ~23 to ~95 K there is a competition between the NTE effect and the electron-phonon interaction. Using the thermal expansion coefficient in the 2 - 300 K temperature range, the thermal expansion contribution to GaAs, at room temperature, represents 21% of the total shift of the excitonic transition energy. After subtracting the thermal expansion contribution from the experimental temperature dependence of the excitonic transitions, in the Al xGa1-xAs alloy, the contribution to the electron-phonon interaction of the longitudinal optical phonon increases, relatively to the longitudinal acoustical phonon, with increasing Al concentration.

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