亚禁带光照对CdZnTe晶体中晶界电场分布的影响  

Influence of sub-bandgap illumination on electric field distribution at grain boundary in CdZnTe crystals

作　　者：陈伟龙 郭榕榕 仝钰申 刘莉莉 周圣岚 林金海 Chen Wei-Long;Guo Rong-Rong;Tong Yu-Shen;Liu Li-Li;Zhou Sheng-Lan;Lin Jin-Hai(Fujian Provincial Key Laboratory of Optoelectronic Technology and Devices,School of Opto-electronic and Communication Engineering,Xiamen University of Technology,Xiamen 361024,China)

机构地区：[1]厦门理工学院光电与通信工程学院,福建省光电技术与器件重点实验室,厦门361024

出　　处：《物理学报》2022年第22期212-219,共8页Acta Physica Sinica

基　　金：福建省自然科学基金(批准号:2020J05239);国家自然科学基金青年科学基金(批准号:51702271)资助的课题。

摘　　要：晶界是限制CdZnTe核辐射成像探测器大面积应用的主要缺陷之一.为了探究改善晶界附近电场分布特性的方式,本文采用Silvaco TCAD从理论上研究了亚禁带光照对于含晶界CdZnTe探测器内电场分布的影响.仿真结果表明,在无偏压下,亚禁带光照能使得晶界势垒降低,从而减小对载流子传输的阻碍作用.在外加偏压下,亚禁带光照使得晶界引起的电场死区消失,使其电场分布趋向于线性分布.同时研究了不同波长和不同强度的亚禁带光照对于晶界电场分布的影响,结果表明光强低于1×10^(-9)W/cm^(2)时,亚禁带光照对于CdZnTe晶体的电场无调节作用.而在波长850 nm,光强1×10^(-7)W/cm^(2)的亚禁带光照下,实现了更平坦地电场分布,因此可有效地提高器件的载流子收集效率.仿真结果为调节晶界电场分布提供了理论指导.Grain boundary is one of the main defects, limiting the large-area application of CdZnTe nuclear radiation imaging detectors. In order to explore the ways to improve the electric field distribution properties near grain boundary, the effect of sub-bandgap illumination on the electric field distribution in CdZnTe detector with grain boundary is studied by Silvaco TCAD simulation technique. The grain boundary potential barrier and electric field dead zone are found in simulation results that significantly affect the carrier transport process in CdZnTe detector. The electric field dead zone caused by the grain boundary disappears under the bias of subbandgap illumination. Thus the electric field distribution tends to be linear. Meanwhile, the effects of different wavelengths and intensities of sub-bandgap illumination on the electric field distribution at the grain boundary are also investigated. The results show that the electric field of CdZnTe is distorted by sub-bandgap illumination at an intensity lower than 1×10^(-9)W/cm^(2). In contrast, a flatter electric field distribution is achieved at a wavelength of 850 nm and an intensity of 1×10^(-7)W/cm^(2). The carriers can be transported by drifting, reducing the probability of being captured or recombined by defects during transport, thus improving the charge collection efficiency of the detector.In addition, the microscopic mechanism of the modulation of the electric field distribution by sub-bandgap illumination and the energy band model of CdZnTe crystal containing grain boundary are proposed. Owing to the existence of the grain boundary, two space charge regions are formed near the grain boundary. The energy band at the grain boundary is bent upward. Meanwhile, the metal-semiconductor contact forms a Schottky barrier, and the energy band near the electrode is bent upward. When the bias voltage is applied, the energy band structure of the CdZnTe tends to tilt from the cathode to the anode. The sub-bandgap illumination can lower the energy band barrier at the

关 键 词：CDZNTE 晶界 Silvaco 亚禁带光照 

分 类 号：O439[机械工程—光学工程] O73[理学—光学]