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 0:2 Ga 0:8 Sb 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 þ 25 meV and E V þ 86 meV, are detected, where E V is the valence band maximum. The density of the E V þ 25 meV acceptor increases with Sb 4 =ðIn þ GaÞ flux beam equivalent pressure (BEP) ratio, whereas the density of the E V þ 86 meV acceptor decreases with increasing BEP ratio. These observations are not consistent with the conventional assumption that these acceptor species are V Sb þ and V Sb 2þ in GaSb-based semiconductors, where V Sb is the Sb vacancy