H trapping at the metastable cation vacancy in α-Ga₂O₃ and α-Al₂O₃

α-Ga₂O₃ has the corundum structure analogous to that of α-Al₂O₃ [1]. The O-H and O-D centers produced by the implantation of H⁺ and D⁺ into α-Ga₂O₃ have been studied by infrared spectroscopy and complementary theory [2]. An O-H line at 3269 cm^-1 is assigned to H complexed with a Ga vacancy (V_Ga), similar to the case of H trapped by an Al vacancy (V_Al) in α- Al₂O₃. The isolated V_Ga and V_Al defects in α-Ga₂O₃ and α-Al₂O₃ are found by theory to have a “shifted” vacancy-interstitial-vacancy equilibrium configuration, similar to V_Ga in β-Ga₂O₃ which also has shifted structures [3-5]. However, the addition of H causes the complex with H trapped at an unshifted vacancy to have lowest energy in both α-Ga₂O₃ and α-Al₂O₃. (α-Ga₂O₃ samples were grown at the Korean Institute of Ceramic Engineering and Technology [6].)

[1] R. Roy et al., J. Am. Chem. Soc. 74, 719 (1952).

[2] A. Venzie et al., Appl. Phys. Lett. 120, 192101 (2022).

[3] J. B. Varley et al., J. Phys.: Condens. Matter 23, 334212 (2011).

[4] A. Krytsos et al., Phys. Rev. B 95, 245202 (2017).

[5] P. Weiser et al., Appl. Phys. Lett. 112, 232104 (2018).

[6] H. Son et al., ECS J. Solid State Sci. Technol. 9, 055005 (2020).