GaN核探测器辐照损伤机制研究

In recent years, wide bandgap semiconductor GaN has attracted a great deal of research interest due to its predominant physical, chemical, and electrical properties. Because of high irradiation hardness of GaN, it becomes a promising material for the new generation of room-temperature nuclear semiconductor detector, especially in the high-radiation field. With the development of GaN nuclear detectors in material growth and process, reliability problems will be put on the agenda, the most important of which is the study of the irradiation damage mechanism. The project bases on the GaN nuclear detectors, and focuses on the effect of radiation defects on the detectors. The relationship between the degradation of performance parameters of detectors and the radiation energy and dose, such as charge collection efficiency, time response, energy spectrum resolution and so on, will be obtained by experiments. The effect of irradiation on the electrical parameters and 1/f noise will be studied deeply, which aims at probing the mechanism of surface states and deep level energies introduced by irradiation to the recombination of non-equilibrium carriers. By the characterization of deep level transient spectrum and photoluminescence spectra at different temperatures, the defects induced by irradiation in detectors are studied. The types, energy levels and capture cross sections of the defects are analyzed in depth. Therefore, the project has the scientific significance in studying and decreasing the radiation damage effects in GaN nuclear detectors. It provides helpful references and bases for both device structure designers and process designers.

宽禁带半导体氮化镓（GaN）因其良好的物理和化学特性，以及优异的抗辐照性能，成为新一代室温核半导体探测器制备领域的热门材料，尤其在强辐射场的探测方面颇具优势。随着GaN核探测器材料生长和工艺制备水平的日趋提高，可靠性问题必然提上日程，首当其冲就是辐照损伤机制研究。本项目立足于GaN核探测器，围绕辐照缺陷对探测器影响展开攻关。通过实验，得到GaN核探测器电荷收集效率、时间响应特性、能谱分辨本领等性能参数退化量与辐照能量、剂量之间的关系。深入研究辐照对GaN核探测器电学参数和1/f噪声的影响，探讨辐照引入表面态、深能级对探测器中非平衡载流子复合的作用机理。通过深能级瞬态谱和变温光致发光谱表征手段，研究辐照在GaN核探测器及材料中引入的缺陷，分析缺陷类型、能级和俘获截面。本项目在研究和抑制GaN核探测器辐照效应方面有重要科学意义，为器件结构和工艺设计者提供有力的参考和依据。

宽禁带半导体氮化镓（GaN）因其良好的特性和优异的抗辐照性能，成为新一代室温核半导体探测器制备领域的热门材料，尤其在强辐射场的探测方面颇具优势。本项目立足于GaN核探测器，围绕辐照缺陷对探测器影响展开攻关。. 本项目完成了高阻HVPE GaN电导型核辐射探测器的研制，并且实现对X射线的超快响应。完成了GaN PIN电流型核辐射探测器的研制与测试，器件漏电为ps级，实现了对α粒子的响应。开展了GaN核探测器响应机理，得到不同反向偏压下电荷收集效率和能量分辨率的变化规律。. 针对电导型核探测器，从表面形貌、晶体质量和发光特性三个方面，对质子辐照前后的HVPE GaN材料进行详细表征。AFM显示质子辐照后HVPE GaN体材料表面粗糙度略微增加。Raman测试结果表明，质子辐照对材料应力和掺杂均无影响，但是声子模FWHM增加，说明中子辐照引起结晶质量的退化。XRD（0002）面2θ-ω扫描曲线FWHM增加，说明引入缺陷密度增加。PL光谱显示，质子辐照后的材料黄带略微增加，而蓝带显著降低。我们认为黄带和蓝带的变化是由于粒子辐照在材料中引入了Ga空位或者与Ga空位相关的络合物缺陷。. 针对PIN电流型探测器，主要研究了快中子和热中子对GaN PIN结构的影响，从I-V、C-V、DLTS、1/f噪声对辐射损伤进行详细表征。显微照片发现热中子辐射对SiO2钝化层造成严重损伤。低反向偏压下，中子辐射载流子去除效应导致反向漏电减小；当反向偏压低于-5V，反向漏电增大，这是由于钝化层损伤、辐射在GaN中引入缺陷、以及金属/GaN界面陷阱引起的；辐射引入复合中心导致正向漏电流的减小。. 本项目获得的GaN核探测器退化规律和辐射损伤表征、机理分析有利于指导器件在辐射环境中的应用。.