High-Pressure High-Temperature Crystallization of GaN: Modeling and Experimental Studies

Using computational modeling, we optimized the resistive heating process of the high-pressure apparatus (HPA) cell designed for the growth of GaN crystals from the Fe–Ga–N solution-melt under high-pressure and high-temperature (HPHT) conditions via the temperature gradient method. The thermal state of the apparatus was simulated by solving the coupled electro- and heat-conduction problem using the finite element method. Modeling determined the spatial distribution of temperature and temperature gradient within the experimental cell. As a result of computational optimization of the thermal state of the toroid-40 type HPA cell, polycrystalline GaN was synthesized from the Fe–Ga–N solution-melt. Reducing the axial temperature gradient in the crystallization volume from 13 to 1.5°C/mm produced the growth of petal-shaped GaN single crystals. Observed crystal growth rates varied from 40 to 250 µm/h.