Shallow Acceptor State in Mg-Doped CuAlO₂ and Its Effect on Electrical and Optical Properties: An Experimental and First-Principles Study

Shallow acceptor states in Mg-doped CuAlO₂ and their effect on structural, electrical, and optical properties are investigated by combining first-principles calculations and experiments. First-principles calculations demonstrate that Mg substituting at the Al site in CuAlO₂ plays the role of shallow acceptor and has a low formation energy, suggesting that Mg doping can increase hole concentration and improve the conductivity of CuAlO₂. Hall effect measurements indicate that the hole concentration of the Mg-doped CuAlO₂ thin film is 2 orders of magnitude higher than that of undoped CuAlO₂. The best room temperature conductivity of 8.0 × 10^-2 S/cm is obtained. A band gap widening is observed in the optical absorption spectra of Mg-doped CuAlO₂, which is well supported by the results from first-principles electronic structure calculations.