Improving the GaN Growth Rate by Optimizing the Nutrient Basket Geometry in an Ammonothermal System Based on Numerical Simulation

The low growth rate of bulk gallium nitride (GaN) when using the ammonothermal method is improved herein by optimizing the nutrient geometry. A numerical model considering the dissolution and crystallization process is developed. Heater powers are employed as thermal boundary conditions to match the real ammonothermal system. The flow field, thermal field, and mass concentration field in the autoclave are calculated with or without a central hole in the nutrient basket. Numerical results show that the mass transfer efficiency and supersaturation on the seed crystal surface can be improved with a hole in the nutrient basket in the center in spite of its diverse effect on the heat transfer, which can be overcome by adjusting the heater powers. As a result, the growth rate of the GaN crystal can be obviously increased.