Optimizing HVPE flow field to achieve GaN crystal uniform growth

•First investigates the influence of gravity on GaN growth in horizontal HVPE reactors.•Change the tilt angle of the seed holder to compensate for the effects of gravity.•Obtain the optimum tilt angle of the seed holder to achieve uniform growth of GaN crystals. In the process of large size GaN crystal growth by hydride vapor phase epitaxy (HVPE), whether the parameters of reactants or the structure of the reactor are changed, the crystal growth is affected by the flow rate and concentration of reactants at different positions in the reactor, namely the flow field in the reactor. Therefore, the crystal quality is very sensitive to the flow field distribution in the reaction chamber. In this paper, the simulation software COMSOL Multiphysics is used to simulate the flow field in the horizontal HVPE reaction chamber. The results show that gravity has an important influence on the uniformity of GaCl and NH3 concentrations on the substrate surface. The method of improving the concentration uniformity of GaCl and NH3 on the substrate surface by changing the different dip angles of the substrate was studied, and the substrate dip angles corresponding to the optimum uniformity of GaCl and NH3 flow fields in HVPE system were obtained. The results were applied to the actual growth, and 2 inch GaN crystals with uniform growth thickness were obtained.