First-principles calculations of intrinsic defects in the p-type semiconductor CuAlO2

Intrinsic defects, including vacancies at the Cu and Al sites (V-Cu and V-Al), substitutional Cu at the Al site (Cu-Al), and interstitial O (O-i), have been proposed to be responsible for the p-type conductivity in CuAlO2. We have investigated the formation energies of these and other intrinsic defects in CuAlO2 using GGA+U calculations. Our results support previous studies that the potential alignment and image charge correction are required in the calculation of defect formation energies by using the supercell approach. In CuAlO2, these p-type defects (V-Cu, V-Al, Cu-Al, and O-i) invariably have lower formation energies than their n-type counterparts. Particularly, VCu and CuAl have the lowest formation energies among intrinsic defects, and therefore are most likely responsible for the p-type conductivity. However, the transition levels of the VCu and CuAl defects are deep, which are responsible for the poor p-type conductivity in CuAlO2.