ALD grown (001) κ-Ga2O3 epitaxial thin films on c-plane sapphire: influence of thickness and thermal annealing
Abstract
Atomic layer epitaxy of high quality κ-Ga2O3 thin films on c-plane sapphire using atomic layer deposition (ALD) offers new opportunities for optoelectronics and power electronics. However, the effects of increasing the number of cycles to increase the κ-Ga2O3 film thickness in the range of 20–100 nm are still unknown. Herein, we study the ALD of the epitaxial (001) κ-Ga2O3 thin film as a function of its thickness by varying the number of cycles from 400 to 2000. Above 20 nm, the epitaxial growth of κ-Ga2O3 thin films with a low surface roughness is preserved with the following relationship: κ-Ga2O3 (001)‖α-Al2O3 (0001), κ-Ga2O3 [010]‖α-Al2O3 [10−10], and κ-Ga2O3 [100]‖α-Al2O3 [11−20]. However, relaxation processes of the epitaxial strain occur, resulting in the formation of multiple rotational domains. Using thermal annealing, a full phase conversion from κ-Ga2O3 to β-Ga2O3 is shown, regardless of the thickness of the as-deposited film. The annealed Ga2O3 thin films grown using 400 cycles remarkably exhibit low surface roughness along with the following epitaxial relationship: β-Ga2O3 (−201)‖α-Al2O3 (0001) and β-Ga2O3 [010]‖α-Al2O3 [10−10]. In contrast, the annealed Ga2O3 thin films grown using 2000 cycles have a higher structural disorder induced by the initial presence of multiple rotational domains. Furthermore, we reveal that the carbon contamination remains negligible both before and after thermal annealing. Eventually, Al/Ga inter-diffusion processes in the proximity of the interface are shown by X-ray photoelectron spectroscopy and transmission electron microscopy after thermal annealing, resulting in the formation of an O-rich region.
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BibTeX
@article{seguret2026grown,
title = {{ALD grown (001) κ-Ga2O3 epitaxial thin films on c-plane sapphire: influence of thickness and thermal annealing}},
author = {Andy Séguret and Ilyass Jellal and Hervé Roussel and Isabelle Gélard and Sonia Ortega Murillo and Laetitia Rapenne and Eirini Sarigiannidou and Fabrice Wilhelm and Andrei Rogalev and Marty Volant and Hanako Okuno and Eva Monroy and Vincent Consonni},
journal = {Journal of Materials Chemistry C},
year = {2026},
month = jul,
doi = {10.1039/d6tc01146b},
url = {https://hal.science/hal-05797161v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - ALD grown (001) κ-Ga2O3 epitaxial thin films on c-plane sapphire: influence of thickness and thermal annealing
AU - Andy Séguret
AU - Ilyass Jellal
AU - Hervé Roussel
AU - Isabelle Gélard
AU - Sonia Ortega Murillo
AU - Laetitia Rapenne
AU - Eirini Sarigiannidou
AU - Fabrice Wilhelm
AU - Andrei Rogalev
AU - Marty Volant
AU - Hanako Okuno
AU - Eva Monroy
AU - Vincent Consonni
PY - 2026
DA - 2026/07/28
JO - Journal of Materials Chemistry C
DO - 10.1039/d6tc01146b
UR - https://hal.science/hal-05797161v1
AB - Atomic layer epitaxy of high quality κ-Ga2O3 thin films on c-plane sapphire using atomic layer deposition (ALD) offers new opportunities for optoelectronics and power electronics. However, the effects of increasing the number of cycles to increase the κ-Ga2O3 film thickness in the range of 20–100 nm are still unknown. Herein, we study the ALD of the epitaxial (001) κ-Ga2O3 thin film as a function of its thickness by varying the number of cycles from 400 to 2000. Above 20 nm, the epitaxial growth of κ-Ga2O3 thin films with a low surface roughness is preserved with the following relationship: κ-Ga2O3 (001)‖α-Al2O3 (0001), κ-Ga2O3 [010]‖α-Al2O3 [10−10], and κ-Ga2O3 [100]‖α-Al2O3 [11−20]. However, relaxation processes of the epitaxial strain occur, resulting in the formation of multiple rotational domains. Using thermal annealing, a full phase conversion from κ-Ga2O3 to β-Ga2O3 is shown, regardless of the thickness of the as-deposited film. The annealed Ga2O3 thin films grown using 400 cycles remarkably exhibit low surface roughness along with the following epitaxial relationship: β-Ga2O3 (−201)‖α-Al2O3 (0001) and β-Ga2O3 [010]‖α-Al2O3 [10−10]. In contrast, the annealed Ga2O3 thin films grown using 2000 cycles have a higher structural disorder induced by the initial presence of multiple rotational domains. Furthermore, we reveal that the carbon contamination remains negligible both before and after thermal annealing. Eventually, Al/Ga inter-diffusion processes in the proximity of the interface are shown by X-ray photoelectron spectroscopy and transmission electron microscopy after thermal annealing, resulting in the formation of an O-rich region.
SN - 2050-7526
SN - 2050-7534
ER -