Hole density and acceptor-type defects in MBE-grown GaSb1-x Bix

We study acceptor-type defects in GaSb1-xBix grown by molecular beam epitaxy. The hole density of the GaSb1-xBix layers, from capacitance-voltage measurements of Schottky diodes, is higher than that of the binary alloys and increases linearly up to 10(19) cm(-3) with the Bi content. Positron annihilation spectroscopy and ab initio calculations show that both Ga vacancies and Ga antisites contribute to the hole density and that the proportion of the two acceptor-type defects vary in the layers. The modification of the band gap due to Bi incorporation as well as the growth parameters are suggested to affect the concentrations of acceptor-type defects.