Optimization of the process parameters for the AlN crystal growth in the PVT method through an improved numerical simulation considering partial pressure of gas phases

Abstract

The growth process is crucial to achieve large-sized and high-quality aluminum nitride (AlN) crystals through the physical vapor transport (PVT) method. To investigate the influence of parameters on the growth of AlN crystals, a series of quasi-steady numerical simulations on the temperature distribution, growth rate, and partial pressure of Al vapor inside the growth cell were conducted based on a self-developed finite element mass transfer module in the COMSOL package, which considers the partial pressure of gas phases, for different growth temperatures and crucible positions. The simulation results show that increasing the growth temperature significantly augments the partial pressure of Al vapor and the growth rate in the growth cell. Simultaneously, variation of the crucible position substantially alters the temperature distribution and the transport direction of Al vapor inside the crucible. A novel heat sink on the top of the crucible was designed to impair the phenomenon of uneven crystal growth on the surface of the seed caused by the nonuniform radial temperature distribution. Compared to the original crucible, the radial temperature gradient of the optimized crucible was reduced by 37%, and the uniformity of seed surface growth was improved by 89%. This work guides the design of a novel crystal growth furnace and the preparation of high-quality AlN single crystals by the PVT method.