Revealing epitaxial relationships at Ga2O3 interfaces with p-type oxides
Abstract
p-type oxide contact layers such as Cr2O3 and NiO are attracting increasing interest in pn-heterojunctions with n-type monoclinic β-Ga2O3 for high-power electronic devices and other extreme environment applications. However, scientific understanding of their epitaxial relationships remains incomplete. In this work we investigate the epitaxial relation of Cr2O3 and NiO layers to (001) and (2̅01) out-of-plane oriented Ga2O3 substrates. Surprisingly, we find that, for the most commercially relevant (001)-orientation of the Ga2O3 substrate, the epitaxial relationships are Cr2O3 (0001) and NiO (111) ∥ Ga2O3 (101), both at the non-intuitive χ = 22.5 ∘ angle with respect to the substrate normal. We explain this unusual discovery by the interfacial atomistic bonding dominated by oxygen sublattice equivalence of these Cr2O3 and NiO polar surface orientations to the tilted Ga2O3 (101), rather than Ga2O3 (001) substrate surface planes. Furthermore, we assign the in-plane orientation for Cr2O3 on (2̅01)-oriented Ga2O3 as: Cr2O3 [123̅0] ∥ Ga2O3 [010] with two in-plane rotational domains. Interface modeling confirms the in-plane orientation for Cr2O3/(2̅01) Ga2O3 and shows that strained O-terminated Ga2O3 (2̅01) surfaces have the lowest interfacial energy with Cr2O3 (0001). Beyond establishing the specific epitaxial relationships for Cr2O3 and NiO on Ga2O3, this work provides a systematic methodology for the unambiguous structural characterization of heterointerfaces involving materials with markedly different crystal symmetries.
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BibTeX
@misc{sacchi2026revealing,
title = {{Revealing epitaxial relationships at Ga$_2$O$_3$ interfaces with p-type oxides}},
author = {Anna Sacchi and Krishna Acharya and Michelle A. Smeaton and Renae N. Gannon and Vladan Stevanovic and Steven R. Spurgeon and M. Brooks Tellekamp and Andriy Zakutayev},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22472},
eprint = {2609.22472},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22472},
}
RIS
TY - UNPB
TI - Revealing epitaxial relationships at Ga_2O_3 interfaces with p-type oxides
AU - Anna Sacchi
AU - Krishna Acharya
AU - Michelle A. Smeaton
AU - Renae N. Gannon
AU - Vladan Stevanovic
AU - Steven R. Spurgeon
AU - M. Brooks Tellekamp
AU - Andriy Zakutayev
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22472
UR - https://arxiv.org/abs/2609.22472
AB - p-type oxide contact layers such as Cr_2O_3 and NiO are attracting increasing interest in pn-heterojunctions with n-type monoclinic β-Ga_2O_3 for high-power electronic devices and other extreme environment applications. However, scientific understanding of their epitaxial relationships remains incomplete. In this work we investigate the epitaxial relation of Cr_2O_3 and NiO layers to (001) and (2̅01) out-of-plane oriented Ga_2O_3 substrates. Surprisingly, we find that, for the most commercially relevant (001)-orientation of the Ga_2O_3 substrate, the epitaxial relationships are Cr_2O_3 (0001) and NiO (111) ∥ Ga_2O_3 (101), both at the non-intuitive χ = 22.5 ^∘ angle with respect to the substrate normal. We explain this unusual discovery by the interfacial atomistic bonding dominated by oxygen sublattice equivalence of these Cr_2O_3 and NiO polar surface orientations to the tilted Ga_2O_3 (101), rather than Ga_2O_3 (001) substrate surface planes. Furthermore, we assign the in-plane orientation for Cr_2O_3 on (2̅01)-oriented Ga_2O_3 as: Cr_2O_3 [123̅0] ∥ Ga_2O_3 [010] with two in-plane rotational domains. Interface modeling confirms the in-plane orientation for Cr_2O_3/(2̅01) Ga_2O_3 and shows that strained O-terminated Ga_2O_3 (2̅01) surfaces have the lowest interfacial energy with Cr_2O_3 (0001). Beyond establishing the specific epitaxial relationships for Cr_2O_3 and NiO on Ga_2O_3, this work provides a systematic methodology for the unambiguous structural characterization of heterointerfaces involving materials with markedly different crystal symmetries.
ER -