Chemical and Physical Rate Processes in GaN Chemical Vapor Deposition

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In this study detailed gas-phase kinetics for the production of GaN films in a chemical vapor deposition (CVD) process will be developed. The focus will be on the homogeneous gas-phase reactions that occur during CVD of GaN from NH3, and trimethylgallium and from NH3 and triethylgallium. Two experimental methods will be used: (1) laser powered homogeneous pyrolysis will be employed for the gas-phase kinetics and (2) optical imaging of vertical concentration profiles above growth surfaces will be used for investigations of important growth species. Reactive intermediate concentration profiles will be imaged using laser induced fluorescence. This experimental program will be complemented with ab initio molecular orbital calculations in combination with transition state theories to estimate rate coefficients for less important reactions not determined in the experimental studies. The gas-phase mechanism developed in this project will be combined with literature information on surface reactions and incorporated into a CVD reactor model. These studies are relevant to the development of GaN light emitting diodes and diode lasers for lighting, for optical data storage and for other applications. GaN is grown commercially by CVD; however, most techniques have been developed by empirical means. This study should contribute to a fundamental understanding of the basic processes.