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

Abstract

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.

Large-Sized GaN Crystal Growth Analysis in an Ammonothermal System Based on a Well-Developed Numerical Model

“…The structure and geometric size of the autoclave are shown in Figure 1. According to our previous research [24], a nutrient basket with a central hole is beneficial for the improvement of the growth rate. Thus, the optimized model is used in this paper.…”

“…Multi-physics fields and their couplings are calculated in the numerical simulation, including flow, heat transfer, and diluted mass transport. The corresponding differential equations can be acquired from [24]. Bossinesq approximation is employed for the calculation of natural convection.…”

Progress in Ammonothermal Crystal Growth of Gallium Nitride from 2017–2023: Process, Defects and Devices

“…Since then, at least two noteworthy papers were published. In the first, Han et al report on a crucible design that is indicated to improve convective flow and gallium uptake in computational fluid dynamics (CFD) simulations [39]. Adding a hole to the center of the basket containing the GaN feedstock, they predict improved nutrient dissolution and transport of gallium-containing species to the growth zone.…”