Rutile GeO2: an ultrawide-band-gap semiconductor with ambipolar doping

TL;DR

This study demonstrates that rutile GeO2 is a promising ultra-wide-band-gap semiconductor capable of ambipolar doping, overcoming key challenges and enabling advanced power electronic devices.

Contribution

Using hybrid density functional theory, the paper identifies doping strategies and growth conditions for rutile GeO2 to achieve ambipolar doping in UWBG semiconductors, a significant advancement.

Findings

r-GeO2 has a band gap of 4.68 eV and can be doped both n-type and p-type.

Low ionization energy donors like SbGe, AsGe, and FO are identified.

Co-incorporation of AlGe with interstitial H enhances hole conduction.

Abstract

Ultra-wide-band-gap (UWBG) semiconductors have tremendous potential to advance electronic devices as device performance improves superlinearly with increasing gap. Ambipolar doping, however, has been a major challenge for UWBG materials as dopant ionization energy and charge compensation generally increase with increasing band gap and significantly limit the semiconductor devices that can currently be realized. Using hybrid density functional theory, we demonstrate rutile germanium oxide (r-GeO2) to be an alternative UWBG (4.68 eV) material that can be ambipolarly doped. We identify SbGe, AsGe, and FO as possible donors with low ionization energies and propose growth conditions to avoid charge compensation by deep acceptors such as VGe and NO. On the other hand, acceptors such as AlGe have relatively large ionization energies (0.45 eV) due to the formation of localized hole polarons and are likely to be passivated by VO, Gei, and self-interstitials. Yet, we find that the co-incorporation of AlGe with interstitial H can increase the solubility limit of Al and enable hole conduction in the impurity band. Our results show that r-GeO2 is a promising UWBG semiconductor that can overcome current doping challenges and enable the next generation of power electronics devices.