COMPARISON OF CDTE, CD0.9ZN0.1TE AND CDTE0.9SE0.1 CRYSTALS - APPLICATION FOR GAMMA-RAY AND X-RAY-DETECTORS

CdTe is one of the most encouraging semiconductor materials in the field of room temperature gamma- and X-ray spectroscopy. To improve the detector properties, the temary systems (Cd,Zn)Te and Cd(Te,Se), and CdTe were grown by vertical Bridgman technique. To achieve low noise detectors, the resistivity of all materials was increased by chlorine doping. The crystals were characterized by electrical (Hall measurements, photoinduced current transient spectroscopy) methods. The numbers of deep levels influencing the resistivity were reduced by introducing Se into the CdTe system. A common deep level close to the middle of the bandgap has been identified, responsible for the compensation effect in all three systems. In addition high resistivity and n-type conductivity were achieved in CdTeSe materials for the first time. Detectors were tested by irradiation with a particles and low gamma-rays. Best charge collection efficiency (CCE) of 91% was recorded for CdTe0.9Se0.1 for both radiation types and smallest FWHM of about 10% at 60 keV.