Numerical Analysis of the High Pressure MOVPE Upside-Down Reactor for GaN Growth

The present paper focuses on the high-pressure metal-organic vapor phase epitaxy (MOVPE) upside-down vertical reactor (where the inlet of cold gases is below a hot susceptor). This study aims to investigate thermo-kinetic phenomena taking place during the GaN (gallium nitride) growth process using trimethylgallium and ammonia at a pressure of above 2 bar. High pressure accelerates the growth process, but it results in poor thickness and quality in the obtained layers; hence, understanding the factors influencing non-uniformity is crucial. The present investigations have been conducted with the aid of ANSYS Fluent finite volume method commercial software. The obtained results confirm the possibility of increasing the growth rate by more than six times through increasing the pressure from 0.5 bar to 2.5 bar. The analysis shows which zones vortexes form in. Special attention should be paid to the transitional flow within the growth zone as well as the viewport. Furthermore, the normal reactor design cannot be used under the considered conditions, even for the lower pressure value of 0.5 bar, due to high turbulences.

Influence of the inlet gas velocity components on the survival of the vertex of gas in the plasma torch

The vortex gas injection into plasma torch is considered as a method for reducing electrodes erosion. In order to investigate the effects of vortex gas injection on plasma structure, as well as the effect of gas viscosity on the rate of rotation, a three-dimensional nonequilibrium and time-dependent non-transferred DC plasma torch model has been simulated. Viewing the general characteristics of the plasma shows that the model works well. The results have shown that if the components of the inlet gas velocity are not properly selected, it is possible that the rotary effects of the gas are greatly depleted even before the gas reaches the cathode tip and plasma formation. In this case, only the change in the axial component of the gas causes changes in the structure of the plasma. Vortex reduction is also observed during the movement of cold gases. It is observed that the change in viscosity of gas has significant effects on the rate of the vortex.