Alkali doping of zinc magnesium oxide alloys for p-type conductivity

Ultrawide-bandgap oxides are usually affected by hole localization, which limits p-type conductivity and inhibits many applications of these materials. Highly localized holes, also known as hole polarons, trap in the vicinity of acceptor dopants, give rise to large ionization energies, and severely constrain free hole concentrations. Wurtzite zinc oxide, in which p-type conductivity has long been sought, exhibits strong hole-trapping behavior. In contrast, the rocksalt polymorph of zinc oxide was found to be resistant to the formation of hole polarons [1]. Moreover, p-type doping using lithium acceptors was predicted to be achievable. However, rocksalt zinc oxide is metastable and has a band gap of only ∼3 eV.

Here, it is found that stable rocksalt zinc magnesium oxide (Zn_xMg_1-xO) alloys are also p-type dopable, in addition to exhibiting band gaps in excess of 4 eV [2]. As in rocksalt zinc oxide, alkali acceptors are shallow in zinc magnesium oxide, and do not appear to be affected by donor compensation. These results indicate that alkali-doped Zn_xMg_1-xO alloys are a promising system for achieving a p-type dopable ultrawide-bandgap oxide.

[1] A. Goyal and V. Stevanovic, Phys. Rev. Mater. 2, 084603 (2018).

[2] J. L. Lyons, arXiv:2507.12446 [cond-mat] (2025).