CdZnTe晶体中深能级缺陷对空间电荷分布特性的影响  

Effect of deep level defects on space charge distribution in CdZnTe crystals

作　　者：郭榕榕 林金海 刘莉莉 李世韦 王尘 林海军 Guo Rong-Rong;Lin Jin-Hai;Liu Li-Li;Li Shi-Wei;Wang Chen;Lin Hai-Jun(Fujian Provincial Key Laboratory of Optoelectronic Technology and Devices,School of Opto-electronics 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》2020年第22期351-358,共8页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:51702271,61904155);福建省自然科学基金(批准号:2020J05239);福建省教育厅中青年教师教育科研项目(批准号:JAT170407)资助的课题。

摘　　要：CdZnTe晶体内的空间电荷积累效应是影响高通量脉冲型探测器性能的关键因素.为了探索CdZnTe晶体中深能级缺陷对空间电荷分布及器件性能的影响规律,本文采用Silvaco TCAD软件仿真了CdZnTe晶体内包含位置为E_v+0.86 eV,浓度为1×10^12 cm^-3的深施主能级缺陷TeCd^(++)时,其空间电荷分布及内电场分布特性.仿真结果表明,随着外加偏压的增加,Au/CdZnTe/Au的能带倾斜加剧,使得晶体内深能级电离度不断增加,空间电荷浓度增加,电场分布死区减小,从而有利于载流子收集.此外,保证CdZnTe晶体高阻的前提下,降低深能级缺陷(Ev+0.86 eV)浓度可使内电场死区减小.深能级缺陷位置为Ev+0.8 eV,亦可以减少阴极附近的空间电荷浓度,使得电场分布更加平坦,死区减小,从而有效地提升载流子的收集效率.Te++Cd CdZnTe recently emerged as a leading semiconductor crystal for fabricating room-temperature x-and gamma-ray imaging detectors,due to its excellent energy resolution and sensitivity.However,its wide deployment is hampered by the low availability of high-quality CdZnTe crystals.As-grown CdZnTe crystals generally encounter the problems arising from the impurities and defects,especially deep level defects.The presence of impurities and defects leads to severe charge trapping,which significantly affects detector performance.Especially for high counting rate imaging detector used in medical imaging and tomography,the accumulation of space charge at deep levels significantly deforms the electric field distribution and subsequently reduces the charge collection efficiency.Therefore,a considerable interest is focused on the investigation of the space charge accumulation effect in CdZnTe crystal,which is the key factor to improve the performance of high counting rate imaging detector.Thus,the goal of this work is to investigate the effects of deep level defects on space charge distribution and internal electric field in CdZnTe detector.In order to reveal the major problem therein,Silvaco TCAD technique is used to simulate the space charge and electric field distribution profile in CdZnTe detector with considering the typical deep level defects in CdZnTe crystals with activation energy of Ev+0.86 eV and concentration of 1×10^12 cm^–3 at room temperature.The simulation results demonstrate that the Au/CdZnTe/Au energy band tilts intensively with the increase of applied bias,which makes the deep level ionization fraction increase.The space charge concentration also increases in the crystal.Meanwhile,the dead layer of electric field distribution decreases,which is of benefit to the carrier collection of CdZnTe detector.In addition,under the premiseof the high resistivity of CdZnTe crystal,the reduction of deep level defect concentration located at Ev+0.86 eV can narrow the internal dead layer moderately.The deep level

关 键 词：CdZnTe核辐射探测器 深能级缺陷 空间电荷 收集效率 

分 类 号：O78[理学—晶体学]