摘要
碲锌镉(CdZnTe)是一种性能优异的室温核辐射半导体探测器材料,广泛应用于核安全、核医学以及空间科学等领域.然而,传统的CdZnTe平面探测器受制于"空穴拖尾"效应的影响,探测性能有待改善.采用改进的垂直布里奇曼法生长的In掺杂Cd_(0.9)Zn_(0.1)Te单晶制备出单载流子收集的4×4像素阵列探测器,通过电流-电压(I-V)测试和γ射线能谱响应测试,研究了像素探测器的电学性能和载流子电输运性能,随之与相应的CdZnTe平面探测器进行了性能对比.结果表明,CdZnTe像素探测器的电阻率约为1.73×10^(10)?·cm,且施加100 V偏压后单像素点的最大漏电流小于2.2 nA;当施加偏压升高至300 V时,单像素点对^(241)Am@59.5 keV的γ射线的最佳能量分辨率可达5.78%,探测性能优于相同条件下制备的CdZnTe平面探测器.
Semi-insulating cadmium zinc telluride（CdZnTe or CZT） is an excellent material candidate for fabricating roomtemperature nuclear radiation semiconductor detectors due to its high resistivity and good carrier transport behaviors.It is widely used in nuclear security, nuclear medicine, space science, etc. Nevertheless, the traditional CdZnTe planar detector is subjected to the effect of ＂hole trailing＂ on its hole transport characteristic, where its energy resolution and the photoelectric peak efficiency both decrease, and thus deteriorating the detection performance. In order to eliminate the effect of hole capture, the electrode with pixel structure for CdZnTe detector is designed for detecting single carriers that are only electrons.In this paper, a 10 mm × 10 mm × 2 mm wafer cut from an In doped Cd_0.9 Zn_0.1 Te single crystal, grown by the modified vertical Bridgman method, is employed to fabricate a 4 × 4 CdZnTe pixel detector, which is composed of 16 small pixel units with an area of 2 mm×2 mm. Each of the pixel units is linked up with ASIC multichannel preamplifier and shaping amplifier by flip chip technology. Finally, the signal is treated by an integrated sensing chip. In the first case,the electrical properties and carrier transport properties of CdZnTe pixel detector are characterized by current-voltage（I-V） measurement via an Agilent 4155 C semiconductor parameter analyzer and γ ray energy spectrum response via a standard Multi Channel Analyzer 6560 spectra measurement system, respectively. In the second case, the differences between CdZnTe planar detector and 4 × 4 pixel detector in the detection performance are discussed in detail. The results indicate that the bulk resistivity of CdZnTe pixel detector is determined to be about 1.73 × 10^（10）？·cm by a linear fit of I-V curve. The maximum leakage current of a single pixel is less than 2.2 n A for a bias voltage of 100 V.Furthermore, the carrier transport behaviors are evaluated with the mobility-lifetime product for electron in CdZnTe detector, which is 5.41×10^-4 cm^2·V^-1 estimated by γ ray energy spectroscopy response under various bias voltages from 50 to 300 V at room temperature. The energy resolutions of the two CdZnTe detectors can reflect the ability of them to distinguish different energy gays during operation. The best energy resolution of a single pixel in CdZnTe pixel detector for ^241 Am@59.5 keV γ ray increases up to 5.78% under a 300 V bias voltage, whereas that of CdZnTe planar detector is only 6.85% in the same conditions. As a consequence, the detection performance of 4 × 4 CdZnTe pixel detector is better than that of the planar detector.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第20期208-214,共7页
Acta Physica Sinica
基金
国家自然科学基金项目(批准号:51502234
51602242)
凝固技术国家重点实验室(西北工业大学)开放课题(批准号:SKLSP201410)资助的课题~~
关键词
碲锌镉
像素探测器
γ射线能谱响应
cadmium zinc telluride, pixel detector, gamma-ray energy spectroscopy response
