Effect of lithium diffusion into Ga2O3 thin films

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• Demonstrated Li diffusion in Ga 2 O 3 epilayers relevant for pn heterojunctions. • Li-diffusion can induce a carrier system in otherwise insulating β-Ga 2 O 3. • Depth-dependent redistribution of deep level defects in Ga 2 O 3 upon Li-diffusion. • Additional Raman mode compatible with the presence of Li in the oxide matrix. • Suggested Li diffusion mechanism in β-Ga 2 O 3 through experiments and theory. The integration of lithium based compounds ( e.g. , Li:NiO/Ga 2 O 3 , LiGa 5 O 8 /Ga 2 O 3 ) in Ga 2 O 3 based pn -heterojunctions raises concerns about interface stability, i.e. , Li diffusion effects on Ga 2 O 3 properties. In this work the ex-situ diffusion of Li is investigated in three different Ga 2 O 3 epilayers systems [(001) κ-Ga 2 O 3 and (−201) β-Ga 2 O 3 heteroepitaxy on (001) α-Al 2 O 3 , and (010) β-Ga 2 O 3 homoepitaxy] at relevant temperatures for the synthesis / processing of Li-based epilayers. It is here experimentally demonstrated and quantified the Li diffusion in all the investigated Ga 2 O 3 epilayers systems and Li bulk ( D Li,bulk ) and 2D defects ( D Li,2D ) diffusion coefficients are provided. In the case of the (010) β-Ga 2 O 3 homoepitaxial layer (nominally free of structural defects), hybrid functional theory calculations foresee a diffusion mechanism mediated by Ga vacancies (V Ga ). Moreover, in the (010) β-Ga 2 O 3 homo-layer a significant effect on its functional properties ( e.g., additional Raman vibrational modes, induced conductivity in an otherwise insulating sample) upon the Li-diffusion process is experimentally highlighted and tentatively related to the passivation of acceptor defects ( i.e. , formation of V Ga - n Li complexes).