新型ZnO单晶半导体核辐射探测器研究

The wide band-gap semiconductors, such as ZnO、GaN、SiC and diamond, have become the front edge and hot spot in the field of radiation detection application due to their main advantages including high breakdown electric field, fast response and good radiation hardness. With the rapid progress of ZnO single crystal technique, fast ZnO scintillator was studied worldwide recently. However, ZnO semiconductor radiation detector is still limited by its lattice defects and large leakage current. In this proposal, the novel semiconductor nuclear radiation detector using high resistivity ZnO single crystal achieved by high temperature heat treatment under oxygen atmosphere is suggested. Through carrying out the study on the lattice defect forming dynamics and the high temperature heat treatment, high resistivity ZnO single crystal for radiation detector can be obtained. By investigating into the response mechanism of ZnO crystal under the nuclear radiation and the trap effect on the excess carriers due to the deep-level defects, the models for the charge collection efficiency, the sensitivity and time response will be built. The optimal structural design and fabrication process of both the photoconductive detector and the fully depleted Schottky diode will be performed to achieve the sub nanosecond pulse detector with high performance. This research job will be of value for initiating the fundamental study of ZnO semiconductor radiation detector and the novel wide band-gap semiconductor radiation detector can be strongly expected in the field of nuclear science and technology.

ZnO、GaN、SiC、金刚石等宽禁带半导体因其高击穿场强、快速响应及强抗辐照特性等显著优势已成为核辐射探测领域的热点和前沿。随着ZnO单晶技术迅速发展，其单晶闪烁体研究近年来被广泛关注，但是受到ZnO半导体缺陷和漏电限制，ZnO单晶半导体核辐射探测器研究尚少。本项目利用氧气氛高温热处理方法获得探测器级高阻ZnO单晶，并重点研究ZnO单晶半导体脉冲辐射探测器。基于本征ZnO单晶点缺陷热动力学形成机制理论，优化高温热处理工艺以获取探测器级半绝缘ZnO单晶；基于高阻ZnO单晶的射线响应机制和载流子的深能级陷阱效应，建立ZnO核辐射探测器的器件物理模型，包括电荷收集效率、灵敏度和时间响应公式；优化探测器结构设计和制作方法，基于光电导结构和肖特基结构实现亚纳秒超快脉冲辐射探测器。该项目对揭示ZnO半导体核辐射探测器响应机理具有重要的研究价值，并为脉冲辐射探测技术领域提供一种新型宽禁带半导体探测器。

基于氧化物缺陷化学理论研究了高温热处理过程中ZnO晶体中施主缺陷和受主缺陷变化趋势，基于高温热处理条件下施主和受主的补偿机制获得了高阻ZnO单晶，900ºC热处理条件下电阻率达到了10^13 Ω·cm；建立基于高阻ZnO单晶的光电导型核辐射探测器的器件物理模型，获得了稳态响应光电流公式和瞬态响应时间依据，通过优化器件结构和工艺，实现了纳秒级响应的ZnO单晶半导体脉冲辐射探测器；研究了ZnO肖特基结和异质pn结型辐射探测器件的制备工艺、响应特性和器件物理，实现了零偏下自供电X射线探测器并且响应时间达到了毫秒级，在反偏条件下实现了跨4个数量级的宽范围线性响应；探索了硅酸锌、氧化银等其它氧化物用于X射线探测的可行性；后续将继续探索具有增益的雪崩型和异质结晶体管ZnO核辐射探测器件。