Growth And Characterization Of Cd_1-xZn_xTe Single Crystals

Cadmium Zinc Telluride (Cd1-xZnxTe or CZT) single crystal is one of the three element compound semiconductor materials with great performances used for the detection of X- ray and gamma-ray at room temperature. It possess many of the physical properties such as high atomic number (Z), large enough band gap, high resistivity, relatively low leakage currents, and high intrinsic mobility-lifetime (UT) product, which are required for room-temperature nuclear radiation detectors. So It is widely used in nuclear medical imaging system, space engineering, and astrophysics, environmental monitoring, and so on. In addition, it is the best substrate for lattice matched epitaxial growth of Hg1-xCdxTe(MCT) thin films and solar cells. But up to now applications of CZT crystal are not yet widely due to the crystals difficulty to grow and their devices fabrication.This paper selected the preferable Bridgman-Stockbarger(B-S) single crystal growth method by comparing with others. Cd-riched is used to control the Cd proportion pressure and to offset loss of the Cd from the crystal. Accompany by anneal, Cd1-xZnxTe single crystals of large bulk (Φ20× (40~50) mm) ,high resistivity (>108 Ω cm) and varied x (x=0.1~0.2)of zinc contentwere steadily obtained by modified Cd-riched unseeded vertical Bridgman method. It is found that speed of 0.4~0.5mm/h, the temperature grads of 8~12C/cm and 4~6% Cd-riched is the preferable condition to grow high quality CZT single crystals.The as-grown crystals were characterization by cutting and directional, X-ray diffraction, high resolution ohmmeter, IR transmission spectroscopy, visible light absorption spectroscopy, scan electronic microscopy (SEM) and positron annihilate time technique (PAT). The IR transmittance of CZT single crystals grown with Cd-riched is about 53%, while 23% with no Cd riched. The positron lifetime spectrograph showed that vacancy type defects are the main defects in as-grown CZT crystals. Based the EAg-I etchant, a new etchant was developed, with which the etch pit pattern on (110), (111) and (100) faces of CZT crystals can emerge immediately and effectually.This pager investigated relation between the (110) faces of cutting from crystals conveniently and accurately by laser reflex method. By the surface treatment, the nuclear radiation detector was fabricated with (110) of CZT crystal and strong 241Am responsibility was observed.