  The presence of defects in the narrow-gap semiconductors GaSb and InSb
affects their dopability and hence applicability for a range of optoelectronic
applications. Here, we report hybrid density functional theory based
calculations of the properties of intrinsic point defects in the two systems,
including spin orbit coupling effects, which influence strongly their band
structures. With the hybrid DFT approach we adopt, we obtain excellent
agreement between our calculated band dispersions, structural, elastic and
vibrational properties and available measurements. We compute point defect
formation energies in both systems, finding that antisite disorder tends to
dominate, apart from in GaSb under certain conditions, where cation vacancies
can form in significant concentrations. Calculated self-consistent Fermi
energies and equilibrium carrier and defect concentrations confirm the
intrinsic $n$- and $p$-type behaviour of both materials under anion-rich and
anion-poor conditions. Moreover, by computing the compensating defect
concentrations due to the presence of ionised donors and acceptors, we explain
the observed dopability of GaSb and InSb.
