CdZnTe晶体中Te相关缺陷的控制方法及高阻晶体电极接触特性的研究

The project will focus on the formation and evolution mechanism of Te related defects in CdZnTe crystal and their effects on the energy resolution of nuclear radiation spectra. The thermodynamic and kinetic data of Te related defects will be explored and then ways to control these defects will be found. The influence of defects with various types and concentrations to the energy response of detectors will also be investigated with the multi-channel energy spectrum measurement, thereby obtaining the effect rule of crystal defects on the energy response spectra and enriching the defect models and theories for high resistivity semiconductor. The concentration and distribution of Te-rich secondary phase, Te antisites and Cd vacancies will attempt to be controlled by the unique three-stage treatment technology and the artificial allocation of defects will be realized. In addition, a novel electrode structure with different transition layers will be proposed and analyzed to prepare electrode on the CdZnTe crystal without or with less carrier traps in contact layer between metal and crystal, providing support for high charge collection efficiency. Eventually, the large-area and 10 mm-thick CdZnTe chips and devices with high efficiency, high gamma-ray spectrometer resolution, and highly uniform charge transport characteristics in the crystal sections will be achieved.

项目研究CdZnTe晶体中以Te相关缺陷为主的微观缺陷的形成和演变机理及其对核探测能量分辨率的影响机制。探明这些缺陷在晶体中的热力学和动力学数据并找出这些缺陷的控制方法，同时结合多道能谱测试等方法分析不同浓度、不同类型的缺陷对器件能谱响应特性的影响，得出晶体中缺陷对器件能谱响应特性的影响规律，丰富高阻半导体晶体的缺陷模型和理论。采用特有的三阶段热处理技术控制和调配Te第二相、Te反位、Cd空位等缺陷的在晶体中的浓度和分布，实现对缺陷种类、浓度分布的人工调控；在电极制备中采用新颖的复合电极结构以及对不同晶面采用适当的过渡层，以获得界面层电子俘获陷阱最少的接触电极，并最终制备出能够用于高效率、高分辨率γ能谱仪的、电荷输运特性在晶体各个部分高度均匀一致的、厚度10mm以上的大面积CdZnTe晶片和器件。

项目基本完成了“获取Te第二相、Te反位、Cd空位等主要缺陷在不同热处理阶段下的行为和动力学数据，获得它们在退火过程中的缩小/长大、解体、重新组合和相互转变等过程中的演变规律。构建出主要缺陷的类化学平衡关系，并据此制定出控制Te第二相、Te反位、Cd空位等主要缺陷的浓度和分布的方法”这一总体目标；通过采用亚禁带光照射的变温光电导实验及PICTS测试结合多道能谱测试达到了“探明各类缺陷与能量分辨率等器件参数的关系和影响机理，丰富高阻半导体的缺陷理论”这一目标；通过梯度热处理方法和三阶段热处理方法的灵活运用，实现了对“缺陷种类、浓度、分布的人工调控，并最终制备出能够用于高效率、高分辨率γ能谱仪的、电荷输运特性在晶体各个部分高度均匀一致的、厚度10mm以上的大面积CdZnTe晶片”；根据对不同电极结构的接触层中的载流子陷阱的研究，获得了“载流子陷阱少，电荷收集效率高的不同晶面的接触电极结构和制备工艺。”