Diffusion of dopants and impurities in β-Ga2O3

Abstract

The understanding and availability of quantitative measurements of the diffusion of dopants and impurities in Ga2O3 are currently at an early stage. In this work, we summarize what is known about the diffusivity of the common donor dopants, Sn, Ge, and Si, as well as some of the deep acceptors, N, Fe, and Mg, and donors, Ir. Two commonly encountered interstitial impurities are H and F, the former through growth and processing ambients and the latter through its use in plasmas used for stripping dielectrics from Ga2O3. Both are found to have high diffusion coefficients and an effect on electrical conductivity, and H shows anisotropy in its diffusion behavior. Si, Ge, and Sn implanted into bulk β-Ga2O3 at total doses from 2 × 1013 to 2 × 1015 cm−2 and annealed at 1100 °C for 10–120 s in either O2 or N2 ambients showed a significant effect of the annealing ambient on the donor's diffusivity. In the case of O2 annealing, there was extensive redistribution of the Si, Sn, and Ge across the entire dose range, while, in sharp contrast, the use of N2 annealing suppressed this diffusion. The N2 ambient also suppressed loss of dopants to the surface, with >90% of the initial dose retained after annealing at 1100 °C for 120 s, compared to 66%–77% with O2 anneals under the same conditions.