A Thermal Transport and Non-Equilibrium Deposition Model in AlN Sublimation Growth Process

Abstract

Sublimation vapor transport method is a widely used technique for production of bulk crystals, such as SiC and AlN. A one-step reaction with two vapor species, i.e. aluminum (Al) vapor and nitrogen (N2) gas, is usually assumed for AlN sublimation growth with diffusion-controlled growth mechanism. However, vapor species generation/consumption is determined by surface reactions, which do not depend on the concentration gradient, but on concentration itself. Thus, the flux at the interfaces is controlled not only by the Fick’s law, but by the surface reaction. In this paper, inductively heated AlN sublimation growth process is simulated to predict the heat generation and temperature field in the growth system. The effects of coil position on heat and mass transfer are investigated. A non-equilibrium growth model considering surface reaction on the source/seed surfaces, diffusion within the boundary layers and vapor transport between source and seed is developed to predict the growth rates at different operating conditions. The predicted results are compared with the experimental data and the results from a traditional diffusion model, which assumes thermodynamic equilibrium on the solid/vapor surface/interface and vapor diffusion through bulk gas. The conditions under which the new model will provide the same as the one obtained by the diffusion model are identified.