In this paper we investigate, computationally and experimentally, the phase stability, electronic structure properties, and the propensity for n-type doping of In$_{ 2}$X$_{ 2}$O$_{ 7}$ (X=Si, Ge) ternary oxides. This family of materials contains promising novel wide-gap semiconductors based on their estimated high $n$-type Baliga figures of merit and acceptable thermal conductivity for power electronics applications. Here, we find that both In$_{ 2}$Si$_{ 2}$O$_{ 7}$ and In$_{ 2}$Ge$_{ 2}$O$_{ 7}$ to be n-type dopable, with Zr providing between 10$^{ 16}$ and above 10$^{ 21}$ cm$^{ -3}$ net donor concentrations under O-poor conditions, depending on the chemistry, structure (ground-state thorvetite or high-pressure pyrochlore) and synthesis temperature. Initial thin-film growth and annealing leads to polycrystalline In$_{ 2}$Ge$_{ 2}$O$_{ 7}$ thin films in thorvetite structure with band gap over 4 eV, and confirms Zr doping predictions by achieving electron concentrations at 10$^{ 14}$-10$^{ 16}$ cm$^{ -3}$ under O-rich condition. While future epitaxial growth development is still needed, this study establishes In$_{ 2}$X$_{ 2}$O$_{ 7}$ as promising n-type wide-gap semiconductors for power electronic applications.
Categories: cond-mat.mtrl-sci