Origin of the 'S-shaped' temperature dependence of luminescent peaks from semiconductors

The 'S-shape' (decrease-increase-decrease) temperature dependence of luminescence peak shift from semiconductors is considered. A luminescence model for the localized state ensemble was employed to interpret this anomalous temperature dependence of the emission peak. The model provides a supplemental contribution from the thermal redistribution of localized carriers to the empirical Varshni relation describing the temperature dependence of the bandgap of perfect semiconductors. Excellent agreement between the theoretical calculation and the experiments was achieved over the whole studied temperature region. The physical origin of the 'S-shaped' shift is revealed.