温度对CdZnTe载流子输运特性和能谱特性的影响

Effect of temperature on the carrier transportation and spectral properties of CdZnTe

采用垂直布里奇曼法生长的CdZnTe(CZT)单晶,制备出单平面探测器。在210～300K温度范围内,测试了不同外加偏压作用下探测器的漏电流,并计算了低压下CZT的体电阻率。同时,在不同电场作用下,测试了CZT探测器对未经准直的241 Am@5.48 MeVα粒子脉冲响应信号的上升时间,计算出电子迁移率为1 360cm2/V-1s-1,并进一步推算出电子寿命随温度的变化规律。在220～300K温度范围内,对比了CZT探测器对241 Am@59.5keVγ射线的能谱响应结果,分析了载流子传输特性及器件性能随温度的变化规律。结果表明,在298～253K温度范围内,降低温度可以提高晶体的体电阻率,减少探测器工作时的漏电流,进而提高探测器的能量分辨率;但当温度低于253K时,电子寿命τe加剧减小,此时由上升时间起伏而引起的全能峰的展宽不能被忽略,导致探测器性能恶化。

Planar detectors were fabricated from single crystal CdZnTe （CZT） grown using the vertical Bridgman method. We tested the leakage current and resistance of the detector under various voltage in the temperature ranges of 210-300 K. Using an un-collirnated 241 Am a particles source with the energy of 5.48 MeV, the mobility of electron was determined to be 1 360 cmZ/V-1 s-1 and the electron-life changing with temperature was estimated. To evaluate the carrier transport behaviors associated with the temperature variation, the pulse spectra of CZT crystals to 241 Am@S0. 5 keV γ-ray were obtained under various bias voltages,in the temperature range of 220--300 K. It is demonstrated that the concentration of the charge carriers is reduced with decreasing the temperature,resuhes in increasing bulk resistivity, and therefore improved the energy resolution is improved. But when the temperature decreased below 253 K,the energy resolution deteriorateds.