Accurate Determination of Acceptor Densities and Acceptor Levels in Undoped InGaSb from Temperature Dependence of Hole Concentration

Without any assumptions regarding residual impurity species and intrinsic defects in an undoped semiconductor, it is experimentally demonstrated that the densities and energy levels of impurities and defects can be precisely determined by a graphical peak analysis method based on Hall-effect measurements, referred to as free-carrier-concentration spectroscopy (FCCS). By FCCS, the number of acceptor species in p-type undoped In_0.2Ga_0.8Sb epilayers is determined, and the densities and energy levels of these acceptor species are accurately estimated. Two acceptor species, whose acceptor levels are E_V+25 meV and E_V+86 meV, are detected, where E_V is the valence band maximum. The density of the E_V+25 meV acceptor increases with Sb₄/(In+Ga) flux beam equivalent pressure (BEP) ratio, whereas the density of the E_V+86 meV acceptor decreases with increasing BEP ratio. These observations are not consistent with the conventional assumption that these acceptor species are V_Sb⁺ and V_Sb²⁺ in GaSb-based semiconductors, where V_Sb is the Sb vacancy.