Wide and Ultrawide-Bandgap Semiconductor Surfaces: A Full Multiscale Model

Germanium, gallium, nitrogen, and oxygen deposition on both GaN(0001) and GaN(0001̄) surfaces were investigated. A multiscale simulation framework was implemented. The DFT simulations were employed to reveal the interactions among the species and GaN surface. Energy diffusion barriers were obtained by the Nudged Elastic Band approach. A Poisson–Nernst–Planck model was implemented to calculate the concentration of each atomic species near GaN surface. The kinetic and unimolecular collision gas theories were incorporated to determine adsorption rates. These outcomes were integrated into a nanoscale kinetic Monte Carlo model. This model allowed to generate data on the surface diffusion and clustering of adsorbed atoms on GaN surfaces. As a result, an enhanced understanding of the deposition and agglomeration mechanisms was achieved. In particular, of the roles played by germanium and oxygen. Due to the relatively high diffusion energy barriers, germanium atoms act as pins around to which gallium atoms tend to cluster. The results align with both experimental observations and existing simulation literature. To the best of our knowledge, no previous DFT simulation results on germanium deposition on GaN have been reported.