用于高粒度时间分辨探测器系统上的低增益雪崩探测器原型的抗辐照性能表征

Radiation hardness characterization of low gain avalanche detector prototypes for the high granularity timing detector

高粒度时间分辨探测器(HGTD)是ATLAS实验Ⅱ期升级的关键项目.为了应对极高的粒子径迹堆积带来的挑战(每次束流交叉对应的质子-质子对撞数的平均值可高达200),合作组计划通过精确测量粒子径迹的时间信息(径迹时间分辨可达30 ps),使得实验能够在"4维"空间中进行粒子径迹到作用顶点的关联.升级项目的传感器选择了可以提供所需的时间分辨率和良好的信噪比的低增益雪崩探测器(LGAD)技术.日本滨松公司(HPK)生产了厚度为35μm和50μm的LGAD原型.中国科学技术大学(USTC)也与中国科学院微电子研究所(IME)合作研发了厚度50μm的LGADs原型.为了评估器件抗辐照性能,样品在JSI反应堆设施中接受了不同剂量的中子辐照,并在USTC进行了测试.通过测量室温(20℃)或-30℃下的电流电压和电容电压曲线测量,对增益层和硅基体损伤的中子辐照效应进行了表征评估.进一步处理提取了不同辐照剂量下的击穿电压和耗尽电压,并呈现为通量的函数,最终对比了不同样品的抗辐照性能参数c系数和α系数.对辐照模型的最终拟合得到的c系数值为HPK-1.2:3.06×10^(-16)cm^(-2),HPK-3.2:3.89×10^(-16)cm^(-2)以及USTC-1.1-W8:4.12×10^(-16)cm^(-2).结果显示HPK-1.2的增益层抗辐照性能最好.此外本文还提出了一种新的方法,进一步从数据中提取了c系数与初始掺杂浓度的关系.

The high granularity timing detector(HGTD)is a crucial component of the ATLAS phaseⅡupgrade to cope with the extremely high pile-up(the average number of interactions per bunch crossing can be as high as 200).With the precise timing information(σt~30 ps)of the tracks,the track-to-vertex association can be performed in the“4-D”space.The Low Gain Avalanche Detector(LGAD)technology is chosen for the sensors,which can provide the required timing resolution and good signal-to-noise ratio.Hamamatsu Photonics K.K.(HPK)has produced the LGAD with thicknesses of 35μm and 50μm.The University of Science and Technology of China(USTC)has also developed and produced 50μm LGADs prototypes with the Institute of Microelectronics(IME)of Chinese Academy of Sciences.To evaluate the irradiation hardness,the sensors are irradiated with the neutron at the JSI reactor facility and tested at USTC.The irradiation effects on both the gain layer and the bulk are characterized by I-V and C-V measurements at room temperature(20℃)or-30℃.The breakdown voltages and depletion voltages are extracted and presented as a function of the fluences.The final fitting of the acceptor removal model yielded the c-factor of 3.06×10^(-16)cm^(-2),3.89×10^(-16)cm^(-2)and 4.12×10^(-16)cm^(-2);for the HPK-1.2,HPK-3.2 and USTC-1.1-W8,respectively,showing that the HPK-1.2 sensors have the most irradiation resistant gain layer.A novel analysis method is used to further exploit the data to get the relationship between the c-factor and initial doping density.