Trap-limited diffusion of Zn in β−Ga2O3

Abstract

Diffusion of Zn in (001)- and (¯201)-oriented β−Ga2O3 was studied using secondary-ion mass spectrometry and first-principles calculations based on hybrid and semilocal functionals. The β−Ga2O3 samples were sealed in quartz ampules together with a piece of metallic Zn and heated to temperatures of 900–1100 ∘C for 1 h. The Zn concentration profiles as a function of depth were simulated by employing the trap-limited diffusion model. From this model the migration barrier for Zn diffusion was found to be Em=2.2±0.2 and 2.1±0.1eV in the (001) and (¯201) orientations of β−Ga2O3, respectively, with corresponding dissociation energies of Ed = 3.5 ±1.1 and 3.2±0.6eV. Results from the first-principles calculations predict an interstitialcy mechanism for the Zn diffusion when it is not in its trapped state. Using the nudged elastic band method, we obtain a barrier of 1.6 eV for migration of Zn split interstitials (Zni) in both the [001] and [¯201] directions, in accordance with the results obtained from the trap-limited diffusion model. Interestingly, the Ga vacancy is found to be able to trap two Zn atoms forming a shallow donor complex labeled ZniZnGa. The energy needed for Zni to dissociate from this donor complex is estimated to be 2.99 eV, in reasonable agreement with the trap dissociation energies extracted from the diffusion model.