Significant sensitivity enhancement of single crystal CdSe x-ray detector by liquid nitrogen cooling

Owing to the large x-ray attenuation coefficient, appropriate bandgap, high resistivity, and high mobility-lifetime (ls) product, binary II-VI semiconductor CdSe is a promising x-ray detection material and it has exhibited excellent x-ray detection at room temperature (RT). For further improving the characteristics of CdSe x-ray detectors, the electrical properties of CdSe single crystals (SCs) grown through the pressureassisted vertical Bridgman method and their x-ray detection performance have been investigated at RT and liquid nitrogen temperature (LNT), respectively. The significantly enhanced x-ray photocurrent and the prolonged response time of the devices operating at LNT indicate the photogenerated carrier lifetime could be increased by the enhanced trapping-detrapping effect obviously, and the mu iota product of CdSe SCs increases from 1.39 X 10(-5) to 5.34 X 10(-4) cm(2) V-1 with temperature lowering from RT to LNT. Meanwhile, an ultrahigh sensitivity of 5.24 X 10(6) mu C Gy(air)(-1)cm(-2) and an extremely low detection limit of 3.68 nGy(air) s(-1) have been acquired by the CdSe SC based x-ray detectors at LNT, which is 140 times higher and 5.8 times lower than it has been at RT. Compared with conventional semiconductor x-ray detectors, the ultra-high sensitivity and extremely low detection limit of CdSe SC based detectors make their application prospects very promising.