AlGaN基p-i-n紫外日盲探测器在雪崩软击穿过程中的损伤机理研究

AlGaN-based p-i-n ultraviolet solar blind avalanche photodiodes(APDs) have the potential to detect very weak signals. However, limited by the high density of threading dislocations in heteroepilayers, they reach the bottle neck. APDs work at the breakdown voltage. The impact ionization avalanche process will initiate damages to the active region. This project mainly investigates the effects of charged threading dislocations in the piezoelectric semiconductor on the behaviors of avalanche soft breakdown. The project aims to understand the damnification mechanism of the active region of APDs during the electron impact ionization avalanche process, and to investigate the roles played by threading dislocations on damnification nucleation and accumulation. Taking the all AlGaN epitaxial structure solar-blind avalanche photodiodes as the research object, TEM electron holography/electron tomography, AFM (surface topography, conductivity micrography, piezo-electric micrography), emission microscope(EMMI), etc., will be combined to investigate the three-dimensional(3D) nature of fields around dislocations. Based on the characterizations of multiple samples, statistics parameters of threading dislocations and their distribution information are obtained, which will be employed to establish a simplified threading dislocation model of the APD chip. Electrical fatigue tests will be designed and conducted. The physical relationship between microscopic damages and macroscopic properties will be established for APDs at different fatigue stages. Through positioning analyses of evolutions of threading dislocations in APDs at different fatigue stages, damnification mechanisms will be deduced. Analytical models and solutions will be established to study 3D distribution of electrical fields associated with different architecture of dislocations and different applied reverse voltages. Using space charges as the media, the theory and experiments will be combined to analyze the double-sides effects of charged threading dislocations on avalanche soft breakdown process. The method of tuning the avalanche soft breakdown behaviors through dislocation architectures will be established, so as to increase APD gains further and decrease the rate of damage accumulation.

AlGaN基p-i-n结构紫外日盲雪崩探测器(APD)有望实现极微弱信号的探测，受制于异质外延的高位错密度，其研究进入瓶颈期。APD工作于击穿电压附近，碰撞电离雪崩过程将诱发损伤。本项目主要研究压电半导体中带电贯穿位错对雪崩软击穿行为的影响，旨在明晰电子碰撞电离雪崩过程对器件有源区的损伤机理及位错在损伤形核、累积中的作用。以正入射全AlGaN外延叠层p-i-n结构日盲APD为研究对象，拟基于TEM电子全息与断层成像、AFM显微、微光显微镜等进行多区域多样品表征，统计分析位错及其分布的特征参数，构建器件内贯穿位错的简化模型；研究微观损伤与器件宏观性能退化的物理关联，定位观测电疲劳试验不同阶段贯穿位错演化规律，分析损伤机理；解析研究不同位错组态、反向偏压下空间电场的三维分布等关键特性；以空间电荷为媒介，理论与实验结合分析位错阵列对雪崩软击穿的双面影响，建立以带电位错组态调控雪崩击穿行为的方法。

本项目系统研究了III-V族氮化物p-MWN-n型发光/探测双功能光电器件中缺陷的表征及其对可靠性影响，执行过程中具体研究方案放弃了成本高、效率低的物理分析方法，如TEM电子全息与断层成像、AFM显微、微光显微镜等，通过与信息论范畴的通信、三维感知和计算机视觉交叉，创新的提出了新型失效分析技术和缺陷的3D立体呈现方法。研究成果能够应用于半导体制造的质量保障；可推广至日盲-红光的宽光谱范围内GaN基光电器件。.本项目设计了一系列不同形状及尺寸的芯片，系统研究尺寸、形状对发光、探测性能的影响，并对比不同透明导电层、不同发光光谱时芯片性能的变化，分析影响发光/探测性能的物理因素。.在此器件基础上，将信息通信领域对信源和信宿器件的表征参数体系（如：频率响应曲线、带宽、误码率等）和实验系统（正交频分复用OFDM调制框架）引入，基于矢量网络分析仪和可见光通信系统给出的光电器件调制特性表征缺陷密度的等级。上述新型测试表征方法，可以兼容于光电器件服役环境，实现器件退化的原位监控。.针对微光显微镜价格高、对缺陷发光的识别能力不足的问题，创新的采用动态视觉传感器搭建主动探测、无损探伤方法，实现1µs的时间精度，提高缺陷识别能力。.针对InGaN、GaN和AlGaN外延叠晶内应力状态与芯片尺寸、厚度的强依赖关系，放弃TEM电子全息方案，采用动态视觉传感器，通过主动调制主动探测得到高时间精度（1µs）的“缺陷发光事件”的稀疏、离散二值时空数据流，利用生物视觉启发的计算机视觉数据处理方法，建模时空分布曲面，通过算法获取缺陷分布信息，建立缺陷分布的亚微观模型。.为了实现缺陷分布的三维可视化呈现，分别针对示教演示开发光场3D显示系统，降低系统对硬件指标，如数据量、刷新频率的要求。.荣获2019年度广东省科技进步一等奖。2020、2021年分两次完成17项发明专利成果转让。