Conductivity Limits in CuAlO₂ from Screened-Hybrid Density Functional Theory

Abstract

CuAlO₂ is a prototypical delafossite <i>p</i>-type transparent conducting oxide (TCO). Despite this, many fundamental questions about its band structure and conductivity remain unanswered. We utilize the screened hybrid exchange functional (HSE06) to investigate defects in CuAlO₂ and find that copper vacancies and copper on aluminum antisites will dominate under Cu-poor/Al-poor conditions. Our calculated transitions levels are deep in the band gap, consistent with experimental findings, and we identify the likely defect levels that are often mistaken as indirect band gaps. Finally, we critically discuss delafossite oxides as TCO materials