Stability, growth, and doping of In${}_2$(Si, Ge)${}_2$O${}_7$ as promising n-type wide-gap semiconductors

Abstract

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.