Studies Of CdSe Single Crystal Growth And Characterization By Vapor Phase Pull Method

Cadmium Selenide (CdSe) is a kind of II A-VIB compound semiconductor materials with broad band gap, it has two crystal structures, The wurtzite structure has large atomic numbers (Z_Cd=48, Z_Se=34, Z_CdSe=41) , rather broad bandwidth(1.74eV), little creepage(at room temperature and high bias voltage), high coefficient of electric charge collect, and can work at room temperature. Compared with CdTe or HgI₂, CdSe has more stable mechanical, thermodynamic and chemical properties. Therefore, CdSe is expected to be used in the area of prospecting, nondestructive examination (NDE), nuclear medicine, environmental detection, safety inspection, and high-energy physics as the substitute of Si, Ge, CdTe and HgI₂.The preparation of CdSe single crystal with high quality and large diameter has become a important subject for many countries.New equipments for crystal growing was designed and large size CdSe single crystal (Φ15mm×40mm) was prepared by the method of vapor phase pull method. CdSe detector was made and tested on ²⁴¹Am-59.5Kev at room temperature.Two zone furnace were designed to adjust temperature field, and a suitable temperature field was obtained for vapor phase CdSe growing.A new technology was adopted: raw purification and crystal growth were proceeded in the same quartz ampoule. Firstly, the raw material was purified in muffle furnace section by section, then the purified material was blocked at the end of the ampoule. Finally, large diameter CdSe was obtained by VUVG. in two zone furnace.Cleavage testing was carried out on CdSe crystal, and two cleavage planes were found: (110) and (100). Oscillating spectrum was obtained by using X-ray diffraction (XRD). Diffraction peaks was Gauss distributed and Full Wave at Half Maximum (FWHM) were 0.585°and 1.862°, which suggested that the CdSe crystal had fine crystallinity. The crystal was analyzed by infrared spectrophotometer.Cleavage testing was carried out on CdSe crystal, and two cleavage planes were found: (110) and (100). Oscillating spectrum was obtained by using X-ray diffraction (XRD). Diffraction peaks was Gauss distributed and Full Wave at Half Maximum (FWHM) were 0.585°and 1.862°, which suggested that the CdSe crystal had fine crystallinity. The crystal was analyzed by infrared spectrophotometer and the result showed that transmission ratio was above 62% in the range of 400cm^-1～7800cm^-1. Ultraviolet spectral analysis revealed that barrier frequency was about 730nm. Forbidden band width was calculated as 1.7eV, and no impurity energy level was observed. The (110) and (100) crystal planes were eroded and pit density was above 1×10 cm^-1. Electrical resistivity of CdSe chip was above 1×10⁹Ω.cm. Metal-semiconductor-metal structured detector was made and tested on ²⁴¹Am-59.5Kev at room temperature. The detector had fine stability and its FWHM was about 10%.Above all, CdSe crystal from VUVG has high quality and is suitable for production of room temperature nuclear radiation detector.