光载流子输运与复合非线性动力学的多寿命分辨与成像表征

Carrier lifetime, the most sensitive parameter to characterize purity, defects, impurities, and interface states of electronic parameters, has direct impact on material performance and device efficiency, and therefore the development of the corresponding characterization techniques has been attracting close attention of electronic information and photovoltaic energy fields. All-optical dynamic non-destructive testing and imaging methodologies based on laser-induced photocarriers have become the main stream worldwide. Currently there are two recognized problems and hot spots: 1) the generally existing nonlinearity in carrier recombination dynamics causes complexity in theoretical modeling, experimental measurements, and self-consistency analysis; and 2) carrier lifetime is a reflection of an effective average over multiple microscopic physical processes, however, different characterization techniques may obtain order-of-magnitude difference in lifetime measurement results due to different ways of averaging and weighting. Based on the Photocarrier Radiometry (PCR) and the Lock-in Carrierography (LIC), this proposal plans to carry out a comprehensive study of the nonlinearity problem in carrier transport and recombination dynamics. A nonlinear theoretical model will be developed based on multi-dimensional experimental data (injection-level, frequency, temperature scans etc.); by introducing waveform engineering and rate-window resonance, multiple carrier lifetimes such as the Shockley-Read-Hall lifetimes, the radiative recombination lifetime, the Auger recombination lifetime, the trap-related capturing cross section and re-emission rates etc. will be resolved and imaged. The proposed all-optical evaluation and imaging methodology is hopeful to provide technical support for the innovation and industrial quality control of information and energy fields.

载流子寿命是表征电子材料纯度、缺陷、杂质、界面态等最灵敏的参数，直接影响材料性能和器件效率，相关检测技术的发展一直受到电子信息和光伏能源领域的密切关注。基于激光诱导载流子的全光动态无损检测与成像技术是国际主流。当前公认难题与研究热点有两个：载流子复合动力学中普遍存在的非线性给理论建模、实验测量、自洽分析造成困难；载流子寿命反映的是多个微观过程的等效平均，而不同表征技术由于平均权重不同导致测量结果可能存在量级差异。本项目基于光载流子辐射测量（PCR）和锁相载流子成像（LIC），针对载流子输运与复合动力学的非线性问题开展系统的理论与实验研究。在多维扫描（注入水平、频率、温度等）的PCR实验数据基础上建立非线性模型；通过波形工程和速率窗口谐振，解析SRH寿命、辐射复合寿命、Auger寿命、陷阱捕获截面和发射速率等多个载流子寿命分布图像，力争为信息和能源领域的创新研究及工业生产提供先进的表征手段。

在高端芯片自主研发与制造领域，我国与发达国家存在的差距不仅体现在研发设计能力与精密制造水平，也体现在先进表征技术的发展与在线质量监控体系的完善。本项目针对半导体载流子输运与复合动力学中普遍存在的多重非线性问题，系统开展了理论和实验研究，为更好地理解和运用光载流子辐射技术和外差锁相载流子成像技术打下了理论基础。.本项目建立了光载流子输运与复合的非线性动力学方程组，针对Shockley-Read-Hall复合、激子辐射复合、Auger复合、陷阱捕获截面和再发射速率等非线性动力学过程进行了精确建模、频域求解、理论仿真、以及实验验证；建立了多载流子寿命的分辨方法以及实验验证；实现了单晶硅晶圆、多晶硅太阳能电池、CdZnTe中红外探测器件、PbS量子点材料与器件的多载流子寿命成像；初步探索了多载流子寿命同材料性质和器件效率之间的关联。.此外，本项目的资助使得一些新想法、新技术、以及应用拓展得到了孵化，包括：半导体晶圆离子注入特性的光载流子辐射表征、基于差分模式的非线性光载流子辐射技术、半导体晶圆电阻率的全光非接触定量测量与空间分布成像、半导体表面处理工艺的非接触定量成像评估等。.有待继续深入开展的研究包括：一、对载流子迁移与扩散过程非线性的精确建模尚未完成，主要源于缺乏非线性偏微分方程以及非线性边界条件的普适数学处理方法；二、在多载流子寿命的反演逆问题唯一性与可靠性的研究工作上较为薄弱，尚未建立从基函数空间结构出发的数学分析手段。.本项目的研究成果所具有的潜在应用方向包括半导体/光电材料与器件特性的全光无损检测/成像以及半导体工艺过程的在线监测两方面。在应对国际半导体工业界新一代表面洁净工艺定量评估的技术需求时，本项目所发展的外差锁相载流子成像技术已经体现出了其定量成像评估以及在线监测的应用潜力；本项目在非线性机理方面的研究成果可以为半导体检测领域的研究同行提供参考；在定量成像方面的研究成果有望为其它无损检测与成像技术的创新提供借鉴和新思路。