Perspective: Towards the predictive discovery of ambipolarly dopable ultra-wide-band-gap semiconductors: the case of rutile GeO$_2$

TL;DR

This paper discusses the potential of rutile GeO₂ as an ultra-wide-band-gap semiconductor with ambipolar doping, highlighting theoretical predictions and recent experimental advances that could enable new power-electronics applications.

Contribution

It introduces rutile GeO₂ as a promising UWBG semiconductor with ambipolar doping, supported by theoretical predictions and recent experimental realization of thin films.

Findings

Rutile GeO₂ is predicted to have an ultra-wide band gap and ambipolar dopability.

Single-crystalline r-GeO₂ thin films have been successfully grown by molecular beam epitaxy.

r-GeO₂ exhibits higher thermal conductivity than β-Ga₂O₃.

Abstract

Ultrawide-band-gap (UWBG) semiconductors are promising for fast, compact, and energy-efficient power-electronics devices. Their wider band gaps result in higher breakdown electric fields that enable high-power switching with a lower energy loss. Yet, the leading UWBG semiconductors suffer from intrinsic materials limitations with regards to their doping asymmetry that impedes their adoption in CMOS technology. Improvements in the ambipolar doping of UWBG materials will enable a wider range of applications in power electronics as well as deep- UV optoelectronics. These advances can be accomplished through theoretical insights on the limitations of current UWBG materials coupled with the computational prediction and experimental demonstration of alternative UWBG semiconductor materials with improved doping and transport properties. As an example, we discuss the case of rutile GeO$_2$ (r-GeO$_2$), a water-insoluble GeO$_2$ polytype which is theoretically predicted to combine an ultra-wide gap with ambipolar dopability, high carrier mobilities, and a higher thermal conductivity than \b{eta}-Ga$_2$O$_3$. The subsequent realization of single-crystalline r-GeO$_2$ thin films by molecular beam epitaxy provides the opportunity to realize r-GeO$_2$ for electronic applications. Future efforts towards the predictive discovery and design of new UWBG semiconductors include advances in first-principles theory and high-performance computing software, as well as the demonstration of controlled doping in high-quality thin films with lower dislocation densities and optimized film properties.