硅光电倍增器的雪崩倍增过程研究

Detection of the low photon flux is one of the crucial problems for the many critical applications, such as nuclear medicine, homeland security, environmental problem, military and other. This problem could not be solved by the traditional methods and technologies of photo-detection. The detection of the low photon flux is possible only with the detection structures which has an internal amplification based on the physical principle to increase the signal produced by the photons in the solid state media as semiconductors. Silicon Photomultipliers (SiPM) is a novel type semiconductor photo-detector based on avalanche multiplication mechanism. It has many excellent characteristics such as high internal gain, high sensitivity, low bias voltage and excellent magnetic compatibility, etc. Silicon photomultiplier at present time is one of the key elements in many critical applications, such as nuclear medicine, experimental physics, space investigations, homeland security and can dramatically increase the progress in that areas. As example silicon photomultiplier is an excellent option for the new generation of the modern medical diagnostic imaging system, in particular Positron Emission Tomography where soon will be important progress. The core technology of silicon photomultiplier is the avalanche multiplication mechanism of semiconductor, but up to now it is not well understood about the avalanche process of silicon photomultiplier structure include the key scientific issue such as the trigger mechanism of the avalanche breakdown and the impact-ionization and transportation process of carriers in the silicon photomultiplier, which seriously hindered the development of silicon photomultiplier technology. The proposed approach of study of possibility of the internal amplification in the semiconductor structures is general representation of the dynamics of the charged particles by the transport equations of one particle distribution function. In this frame on base of using the kinetic approach can be derived the difference schemes for the macroscopic parameters, describes the behavior of the electron hole carriers in the semiconductor structures for the avalanche processes. The study included the investigation of the theoretical model and detailed study of creating the electrons with the photoelectric interaction processes, processes of the amplification of the free carriers in the semiconductor structure by the strong electric field, processes of the propagation avalanche of charged particles in the semiconductor material. The project is detailed study of the avalanche processes in the semiconductor structures for the purposes of the detection low photon flux in Silicon Photomultiplier, establish the theoretical and practical basis of the avalanche amplification processes in the semiconductor structures for the detection of the low photon flux and development of the technology for the low photon flux detectors – Silicon Photomultiplier.

硅光电倍增器（Silicon Photomultiplier，简称SiPM）是一种有潜力带来光电探测行业巨大革新的新型半导体光电探测器件，其技术核心是盖革模式雪崩倍增机制。但至今SiPM结构中雪崩倍增机制包括雪崩过程发生条件以及载流子在雪崩倍增条件下的碰撞、离化、传播过程等关键科学问题还没有被清晰的理解和解释，这极大地阻碍了SiPM技术的发展。本课题基于磁气动力学的宏观参数差分格式方法，以光子在SiPM中的吸收及载流子碰撞离化的物理机制为研究对象，对SiPM的雪崩倍增过程进行深入研究。研究内容包括：光子在半导体材料中光电转换率大小的影响因素、载流子在内部强电磁场中的离化机制和传播形式，建立包含硅材料特性、光量子属性、载流子运动过程的多因素复合模型。旨在揭示SiPM进行弱光探测的雪崩倍增过程的物理机制，为有效解决SiPM弱光探测效率低的难题和研制出新型的光电探测器SiPM奠定理论和技术基础。

硅光电倍增管(SiPM)因其高增益，低偏置，紧凑且体积小等优势在过去五年中成为了从汽车到医疗等众多领域的关键传感器。其技术核心是盖革模式雪崩倍增机制。然而，由于对SiPM结构中雪崩倍增机制理解不够明确，SiPM技术的发展受到限制。申请人基于磁气动力学的宏观参数差分格式方法，研究了雪崩过程发生条件以及载流子在雪崩倍增条件下的碰撞、离化、传播过程等，揭示了SiPM 进行弱光探测的雪崩倍增过程的物理机制。基于对SiPM结构中雪崩倍增机制的深入理解，研制出了首个标准CMOS工艺的SiPM芯片，解决了SiPM弱光探测效率低的难题。其在420 nm波长处的光子检测效率高达40%，单光子时间分辨率约为70 ps(FWHM)。申请人将新型SiPM引入到应用专用型数字PET系统中，取得了积极成果，如质子治疗监测系统、数字脑PET系统及数字小动物PET系统等，均获得了具有最佳性能的掺杂曲线，首次证实了基于CMOS的SiPM传感器在PET应用中具有极大的优势。本项目建立了雪崩倍增机制理论基础，研制了高光子检测效率、高分辨率的首个标准CMOS工艺SiPM芯片，发展了相关应用，实现了从理论到关键核心器件再发展应用的完整技术路线，拓展了SiPM在应用方面的深度和广度。