  We report first-principles calculations that clarify the formation energies
and charge transition levels of native point defects (Ga and O vacancies,
interstitials, and a Ga vacancy-O vacancy pair) in corundum structured
${\alpha}$-Ga2O3. Either under a Ga- or O-rich growth condition, the
negatively-charged Ga vacancy and the positively-charged Ga interstitial on a
site surrounded by six O atoms are dominant when the Fermi level approaches the
conduction and valence band edges, respectively. These defects would compensate
carrier electrons and holes, respectively. Ga-rich conditions relatively
suppress the formation of the Ga vacancy and, therefore, are suited for
extrinsic n-type doping of ${\alpha}$-Ga2O3.
