A benchmark study on tetravalent ion doping in heteroepitaxial β-Ga2O3 films fabricated by pulsed laser deposition

Tetravalent ion doping is widely used in modulate the electrical properties of β-Ga2O3, but the effectiveness of different dopants and the transport behavior vary significantly among different studies. Herein, we benchmark the doping impact of commonly used tetravalent ion dopants on the lattice structure and transport behavior of β-Ga2O3 films. Specifically, epitaxial β-Ga2O3 films on MgO (001) substrates with different donor dopants (Si, Sn, Zr, Hf) are fabricated by pulsed laser deposition (PLD) under the identical growth conditions. It is found that the incorporation of Si, Zr and Hf could improve the crystallization of β-Ga2O3 films, while the Sn doping degrades the film crystallinity. Moreover, the doped Ga2O3 films exhibit larger carrier concentrations (1019 cm−3) by introducing Si, Zr or Hf, followed by the undoped films (1018 cm−3) and then Sn-doped Ga2O3 film (1017 cm−3). The XPS measurement reveals the appearance of Sn2+ ions in Sn-doped films, which is account for the observed poor crystallization and worse conductivity. The versatile variable-valence state of the Sn element could be a common issue for β-Ga2O3 films fabricated by vacuum-based physical vapor deposition methods. This study identifies the use of Si, Zr and Hf dopants as effective ways to obtain n-type conductive Ga2O3 films for optoelectronic and power electronic devices.