Temperature dependent optical absorption in hydrogenated silicon from amorphous to crystalline state

The optical absorption of hydrogenated silicon has been determined at low and elevated temperatures from 4 to 973 K for several amorphous and crystalline states obtained by annealing. The variation of the optical gap is deduced using the Tauc model and then interpreted using the Varshni relation. In the energy range considered, the absorption coefficient increases exponentially with temperature. A characteristic thermodynamic function such as heat capacity C(T) has been calculated using parameters occurring in the Varshni relation. This is shown to illustrate the differences between the amorphous states obtained during annealing.