Deuterium incorporation and diffusivity in plasma-exposed bulk Ga2O3

Abstract

Deuterium incorporation depths of ∼0.13–0.65 μm were obtained in bulk, single-crystal Ga2O3 during exposure to 2H plasmas for 0.5 h at 100–270 °C. The data were fit using the Florida Object Oriented Process Simulator simulation code. The estimated diffusivities were in the range of 2.3 × 10−14–6 × 10−13 cm2/V·s over this temperature range. The activation energy for diffusion was 0.30 ± 0.08 eV, suggesting that the diffusing deuterium migrates as an interstitial. The solubility of the deuterium exhibited an activation energy of 0.35 eV. Subsequent annealing at 500 °C removed ∼85% of the deuterium out of the Ga2O3, with an activation energy of 1.35 eV. This indicates that the outdiffusion is mediated through defects or molecule formation. The thermal stability of deuterium retention is lower (∼150 °C shift to lower temperatures) than when the deuterium is incorporated in the Ga2O3 by direct ion implantation, due to trapping at residual damage in the latter case. The incorporation depths of deuterium in the Ga2O3 are significantly less than in bulk ZnO under the same conditions, where we observed incorporation to ∼25 μm.