Materials Development for Boron Phosphide Based Neutron Detectors: Final Technical Report

Edgar, James Howard¹ 

[1]Kansas State Univ., Manhattan, KS (United States)

关键词: BORON PHOSPHIDES;    CRYSTAL GROWTH;    EPITAXY boron phosphide;    neutron detection;    silicon carbide;    crystal growth;    epitaxy;   

DOI  :  10.2172/1156590
RP-ID  :  DOE-KS ST Univ 09132014
PID  :  OSTI ID: 1156590
Others  :  Other: None

美国|英语

来源: SciTech Connect

【 摘 要 】

The project goal was to improve the quality of boron phosphide (BP) by optimizing its epitaxial growth on single crystal substrates and by producing bulk BP single crystals with low dislocation densities. BP is potentially a good semiconductor for high efficiency solid state neutron detectors by combining neutron capture and charge creation within the same volume. The project strategy was to use newly available single crystal substrates, silicon carbide and aluminum nitride, engineered to produce the best film properties. Substrate variables included the SiC polytype, crystallographic planes, misorientation of the substrate surface (tilt direction and magnitude) from the major crystallographic plane, and surface polarity (Si and C). The best films were (111)BP on silicon-face (0001) 4H-SiC misoriented 4?�� in the [1-100] direction, and BP on (100) and (111) 3C-SiC/Si; these substrates resulted in films that were free of in-plane twin defects, as determined by x-ray topography. The impact of the deposition temperature was also assessed: increasing the temperature from 1000 ?��C to 1200 ?��C produced films that were more ordered and more uniform, and the size of individual grains increased by more than a factor of twenty. The BP films were free of other compounds such as icosahedral boron phosphide (B₁₂P₂) over the entire temperature range, as established by Raman spectroscopy. The roughness of the BP films was reduced by increasing the phosphine to diborane ratio from 50 to 200. Bulk crystals were grown by reacting boron dissolved in nickel with phosphorus vapor to precipitate BP. Crystals with dimensions up to 2 mm were produced.