Purification, growth, fabrication and characterization of wide bandgap materials. Final technical report

Wide bandgap semiconductor single crystals, such as heavy metal halide compounds, have been grown by physical vapor transport and Bridgman methods. Zone-refining and vacuum sublimation techniques were used to purify and adjust the stoichiometric composition of the starting material, and were proven to be effective. Several spectroscopic, microscopic and thermodynamic analytical techniques were employed to investigate the optical, electrical and structural properties of crystals. These results revealed information regarding micro- and macroscopic defects, impurities and modifications resulting from source material, growth process, post-growth treatment and device fabrication. Crystal growth and processing conditions have been correlated with this information and were optimized to achieve the purest and highest quality materials for practical device applications. Future works will involve optimization of material purification and crystal growth processes to produce high purity and low defect crystals, development of sensitive material characterization tools allowing a better understanding of defects formation and their correlation with processing conditions. Developments in bulk crystal growth research for detector devices in the Center for Photonic Materials and Devices since its establishment have been reviewed. Purification processes and single crystal growth systems employing physical vapor transport and Bridgman methods were assembled and used to produce high purity and superior quality wide bandgap materials based on heavy metal halides semiconductors. Comprehensive material characterization techniques have been employed to reveal the optical, electrical and thermodynamic properties of crystals, and the results were used to establish improved material processing procedures