Anisotropic and trap-limited diffusion of hydrogen/deuterium in monoclinic gallium oxide single crystals
Vilde Mari Reinertsen, Philip Weiser, Ymir Kalmann Frodason, Marianne Etzelmüller Bathen, Lasse Vines, K. M. Johansen
Abstract
The effect of lattice anisotropy on the diffusion of hydrogen (H)/deuterium (2H) in β-Ga2O3 was investigated using secondary ion mass spectrometry (SIMS) and hybrid-functional calculations. Concentration-depth profiles of 2H-implanted single crystals show that 2H can diffuse along the direction perpendicular to the (010) surface at temperatures as low as 300 °C, whereas diffusion along the direction perpendicular to the (-201) surface occurs only around 500 °C. For both directions, the evolution of the 2H concentration–depth profiles after heat treatments can be modeled by trap-limited diffusion. Moreover, the traps can be present in the as-received crystals or created during ion implantation. Comparison of the experimentally obtained binding energy for 2H to the trap (2.3 ± 0.2 eV) with the binding energies determined from first-principles calculations suggests that intrinsic point defects (e.g., VGaib) or defect complexes (e.g., VGa(2)VO(2)) are excellent candidates for the trap and will play a crucial role in the diffusion of H or 2H in β-Ga2O3.