Bi(III)‐based oxide semiconductors with ambipolar doping: (Na, K)BiO2

Abstract Bi(III)‐based oxides are emerging as important semiconductors for future electronic applications. Through hybrid density functional theory calculations and defect analysis, we demonstrate that A Bi(III)O 2 ( A = Na or K) is a promising wide‐band‐gap bipolar semiconductor. Our calculations predict A BiO 2 to have a large band gap of 1.97 eV for NaBiO 2 and 2.77 eV for KBiO 2 . Unlike widely‐used oxide semiconductors such as In 2 O 3 and ZnO, the spatially extended cation states (Bi 6s) of A BiO 2 significantly contribute to the valence band maximum, enhancing p‐type dopability. We indeed show that potential acceptors, such as Sr Bi , produce shallow levels. In addition, n‐type doping is found to be possible through the extrinsic doping of heterovalent elements such as Te and F. The band‐structure analysis reveals that A BiO 2 has small effective masses for electrons and holes (< 1 m 0 where m 0 is the electron rest mass), indicating favorable electron and hole transport properties.