Predictive calculations of electron and heat transport in ultra-wide-band-gap semiconductors

Ultrawide-band-gap semiconductors are used for energy-efficient power electronics, but there is a pressing need to imrpove on current materials. Beta gallium oxide (β-Ga₂O₃) outperforms materials such as Si, SiC, and GaN due to its wide band gap and corresponding large breakdown field. However, three drawbacks of β-Ga₂O₃ are its lack of p-type doping, its low thermal conductivity, and its inferior electron mobility. Using first-principles calculations we calculate the electron-phonon coupling of β-Ga₂O₃ to understand the origin of the limits to the electron mobility and thermal conductivity. We also explore rutile germanium dioxide (r-GeO₂) as a semiconductor for power-electronic applications. The calculated band gap and optical absorption spectrum is in good agreement with optical measurements. We also determine the phonon-limited carrier mobilities and lattice thermal conductivity as a function of temperature and crystal orientation. We find that the electronic and thermal transport properties of r-GeO₂ outperform current materials, while it can also be ambipolarly doped. Our results highlight the potential of r-GeO₂ for power electronics.