Temperature dependence of the indirect bandgap in ultrathin strained silicon on insulator layer

Photoluminescence spectroscopy is applied on tensely strained silicon on insulator layer in order to evaluate the temperature dependence of the indirect energy bandgap. The strained silicon indirect bandgap follows a similar behaviour to bulk silicon at high temperature (from 80 K up to 300 K) which was described from the Varshni [Physica 34, 149 (1967)] and Bose-Einstein equations. Nevertheless, at low temperature (from 9 K to 80 K), an unusual blueshift of the bandgap is evidenced. The latter can be modelled considering band-tail states of density of states which are related to the strain fluctuation.