MOVPE growth and thermal treatment of gallium nitride and indium nitride

Group III-nitride compound semiconductor materials have been actively investigated for the past decade because of their importance in short wavelength photonics and high temperature, high frequency electronic devices. In this research, it was found that a SiOxN1-x compliant interface was able to relieve stress at the substrate-film interface. It was shown experimentally and verified by thermodynamic analysis that initial GaN growth at low-temperature prevented the formation of Si3N 4, which prevents GaN epitaxy. Also, it was shown that subsequent thermal annealing improves the quality of low-temperature-grown GaN significantly, compared to the high-temperature-grown film.; Growth of InN using MOVPE has several challenges. The growth temperature is limited to the range of 450∼600°C because of the high vapor pressure of nitrogen over InN and low dissociation rate of NH3. A high V/III ratio (>104) is usually required to prevent In droplet formation at growth temperature. A novel method was tested to prevent co-deposition of In. A post growth thermal annealing in a stream containing HCl/N2 revealed that the droplets disappeared selectively at 550°C. A chemical equilibrium analysis showed good agreement with the experimental results. It was also shown that InN could be grown at low V/III ratio (∼2500) without in co-deposition in presence of HCl.; Interdiffusion in the GaN-sapphire, silicon, and lithium gallate systems was studied using SIMS and consecutive annealing. Gallium nitride films were grown by low-pressure MOVPE on (0001) Al2O3, (111) Si, and LiGaO2 (100) at 850°C. The films were then annealed at growth temperature in the time range 30 to 120 min. Diffusion coefficients were estimated by fitting to the 1-D Fick's law. The Ga diffusion coefficients into sapphire, silicon, and lithium gallate are 4.81 x 10-17 , 2.92 x 10-17, and 1.46 x 10 -17 cm2/s, respectively. The Al, Si, and Li diffusion coefficient into GaN are 3.98 x 10-17, 3.70 x 10-17, and 2.48 x 10-17 cm 2/s, respectively.; The impact of interdiffusion on strain energy in the GaN-sapphire system was studied. A model was developed to predict the strain energy and describe its relaxation behavior. The calculations assume a gradual transition of lattice parameter near the interface rather than an abrupt transition. The effect of interdiffusion on the strain energy and predicted critical thickness was clearly demonstrated.; The polarity of the film has a strong influence on the morphology and the optical properties of PA-MBE grown As-doped GaN layers. Strong blue emission from As-doped GaN was observed only in the case of N-polarity (000-1) layers, which was attributed to the highest concentration of Ga dangling bonds for this polarity of a GaN surface.