Experimental investigation of the epitaxial lateral overgrowth of gallium nitride and simulation of the gallium nitride metalorganic chemical vapor deposition process.

摘要

In this dissertation, the experimental investigation of the epitaxial lateral overgrowth of GaN and the simulation of the GaN MOCVD process are presented.; The effects of various parameters on the MOCVD and ELO process were examined. The crystal structures of both the GaN seeding layers and the ELO layers were examined by XRD &thetas;-2&thetas; scan and x-raying rocking curve. Significant film morphology improvement has been achieved by the ELO process. It was found that V/III ratio has no significant effect on GaN film growth in the MOCVD process. The use of a low temperature GaN buffer layer in the ELO process gave the best quality GaN film. The AIN buffer layer was found not suitable for the second growth of GaN from the seeding layer openings.; The modeling of the GaN MOCVD process has given a deep understanding of the growth process. Kinetic model describing both gas-phase and surface reactions were used in the simulation. The effect of thermal diffusion and radiative heat transfer were also taken into account. The transport phenomena for the gas mixture in the reactor chamber were studied under different operating conditions, such as susceptor rotation speed and ammonia flow rate at inlet, in different inner tube configurations. A detailed analysis of the reactions and transport process was given. The bell-shaped inner tube configuration was predicted to give better growth rate distribution than the other two configurations. High susceptor rotation speed increases the film growth rate on the substrate, but very high susceptor rotation speed also decreases the desorption rate of the surface reaction products from the growth surface. The simulation also indicated that an optimal ammonia flow rate exists. The model was validated by experimental data, and was used to explain the observed unwanted deposits on the inner tube wall for the bell-shaped inner configuration.