Electronic structure of p-type transparent conducting oxide CuAlO2

Copper-based delafossite oxides are excellent candidates for the p-type transparent conducting oxide (TCO), which is essential in realizing transparent semiconductor applications. Using angle-resolved photoemission spectroscopy (ARPES), we report the low-energy electronic structure of CuAlO₂. We found that the band structure near the valence band top is characterized by hole bands with their maxima along the Brillouin zone boundary. Furthermore, the effective masses along the Γ–M and Γ–K directions were found to be (0.6 ± 0.1) m₀ and (0.9 ± 0.1) m₀, respectively, which impose an important benchmark against the existing band calculations.