DFT mechanistic insights into the atomic layer deposition of β-Ga2O3

Abstract

Ga₂O₃ is a wide bandgap semiconductor material exhibiting vast application potential in power electronics, radio frequency electronics, deep ultraviolet optoelectronic devices, and other fields. The fabrication of β-Ga₂O₃ thin films presents a formidable yet indispensable task although a multitude of epitaxial growth techniques has been utilized, with chemical vapor deposition (CVD) and atomic layer deposition (ALD) being the most prevalent. However, the growth mechanism of β-Ga₂O₃, especially through ALD using trimethyl gallium (TMG) and O₂, is still poorly understood. Thus, in this study, we employ density functional theory (DFT) to investigate the surface reaction mechanisms and detailed pathways of β-Ga₂O₃ ALD with TMG and O₂ as the precursors. The process consists of two self-limiting half-reactions, TMG chemisorption and O₂ oxidation, which collectively enable a layer-by-layer growth. Our computations reveal that the methyl groups in TMG undergo progressive dissociation and hydrogen transfer, ultimately desorbing as stable gaseous products such as CH₄ and C₂H₄. These results provide atomistic insights into the key intermediates and energy barriers governing the ALD process, facilitating a better control over the film properties and offering a general framework for mechanistic studies in metal oxide ALD.