Vapor Transport Controlled Process Models for AlN Bulk Sublimation Growth

Sublimation vapor transport method is a widely used technique for the production of optoelectronic materials, such as AlN single crystals. Inductively heated method is most commonly used in high temperature materials processing. In the literature, a one-step reaction with two vapor species, i.e. aluminum (Al) vapor and nitrogen (N₂) gas, is usually assumed and a diffusion-controlled growth mechanism is used with thermodynamic equilibrium calculations. In the growth experiments, crystal growth may be in the kinetic controlled region, the interplay between surface kinetics and vapor transport is important. Temperature field with inductively heated method will be simulated in this paper. Afterwards, three growth models are proposed. One model is called the traditional model assuming thermodynamic equilibrium and diffusion as the rate-limiting process, and two other models are developed based on equilibrium partial pressure of either aluminum vapor or reaction nitrogen gas. The predicted growth rates by three models are compared. The advantage and disadvantage of different models are discussed.