Very low temperature TSC trap spectroscopy

Abstract

In a previous paper (1980) showed that differential TSC spectroscopy enables them to discriminate easily between a monomolecular and a bimolecular recombination process. It was also deduced that it leads to a correct evaluation of the coefficient X=E_t/kT_m relating the activation energy E_t and the temperature T_m of the maximum (20<X<30). In the present work they examine the particular case of the TSC peaks lying at very low temperature (below 77K): the temperature dependence of the thermal velocity and of the density of states in the band introduce an important correction leading to values of X that can be lower than 10. The corresponding activation energies are then much lower than the values deduced from the usual Urbach's law. The experimental case of semi-insulating GaAs is studied: four overlapping peaks are found in the range 10-50K that could correspond to donors or acceptors impurities (10-50 meV). These low activation energies are confirmed by a fractional emptying experiment.