LAUSR

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 alt;iagt;αalt;/iagt;-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;. 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 alt;iagt;αalt;/iagt;-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;.