The Numerical Simulation Study On Growth Of GaN By Vertical HVPE System

Based on the Computational Fluid Dynamics(CFD), the Hydride Vapor Phase Epitaxy(HVPE) of GaN in a vertical flow reactor was studied in this paper by using finite element method. Experiments using CFD software will save the cost and it also provide theoretical principle for the optimization GaN reaction chamber, so computational fluid dynamics software have a lot of guiding significance to the actual process of the growth of GaN.The influence of the substrate height(the vertical distance between GaCl outlet and the substrate) on the distribution of GaCl and NH3 molar concentration was studied with two-dimensional simulation.By a set of experimental models, The distance between outlet and substrate are not the same. Comparison of the growth rate and the distribute of GaN from different models to get the best distance. In the end of the experiment we found the best substrate height is 15 mm.The influence of the nozzle diameter on the growth of GaN was studied with two-dimensional simulation. We set two-step process to get the best results. First we set the diameter of N2 tube to be fixed, and change the outlet area of NH3 and GaCl to get first solution, then we change the out area of N2 to get another solution. The inner diameter of GaCl outlet is 12 mm, the internal diameter of NH3 is 43 mm and the inner diameter of N2 is 76 mm. These are the best diameter settings.Individually adjusting the distance between GaCl outlet and substrate will have an effect on the diffusion of NH3 and GaCl.When the distance is too close, GaCl outlet nozzle will prevent NH3 spread to the substrate.But if the distance is too far it will let some NH3 into the GaCl outlet nozzle. Neither situation is good for the growth of GaN. The growth rate of GaN was very fast and uniform when distance between GaCl outlet and substrate is 17 mm.