Calculation, measurement and control of the energy barriers and the light-induced kinetics of the A_Si-Si_i defect

硅基光电子器件作为太阳能电池或探测器是我们日常生活的一部分，因此在正常工作模式下由光或电荷载流子引起的逐渐退化具有技术和经济重要性。欧洲核子研究中心的硅基粒子物理辐射探测器就是一个很好的例子。为了制定适当的策略来避免功能丧失，必须了解光诱导产生的缺陷和降解的动力学。这就是研究项目的开始。研究了光致缺陷中的一种典型缺陷--A_Si-Si_i缺陷。该缺陷由受体原子（例如，硼或铟）和相邻间隙位置上的硅原子。在实验和理论的密切配合下，对这类缺陷有一个全面的认识。其目的是最终解决文献中存在的差异，提出的结构模型的基础上，实验数据和理论推导的模型。此外，将检查工作假设，即B_Si-Si_i缺陷是所谓的硼-氧-光诱导退化（BO-LID）的原因。为此，应通过实验分析缺陷的结构和动力学，同时从理论上进行描述。例如，计算的势垒高度之间的两种状态的缺陷应与三种不同的实验方法的结果进行比较。这些是低温光致发光光谱，电子自旋共振光谱，和微波检测载流子寿命测量的光电导衰减。进行各种硅样品的退火，目的是以受控的方式控制缺陷。为此，首先制备具有最高可能缺陷密度的样品，因此预期会有强信号。目标退火协议旨在实现缺陷密度的持续降低。从技术的角度来看，这可以用来抵消由于辐照而导致的效率损失的问题。然而，该研究项目的主要目标是对A_Si-Si_i缺陷、其结构和动力学以及缺陷诱导的电荷载流子复合进行基本和全面的微观理解和模型。

Silicon-based optoelectronic devices are part of our everyday life as solar cells or detectors and their gradual degradation induced by light or charge carriers in normal operation mode is therefore of technological and economic importance. The silicon-based particle physics radiation detectors at CERN provide a drastic example. In order to work out adequate strategies to avoid the loss of function, the light-induced generation and kinetics of the defects underlying the degradation have to be understood.This is where the research project starts. It investigates the A_Si-Si_i defect, an important and exemplary type of light-induced-defect. This defect consists of an acceptor atom (e.g., boron or indium) on a regular lattice site and a silicon atom on an adjacent interstitial site. In close cooperation of experiment and theory, a comprehensive understanding of this kind of defects shall be worked out. The aim is to finally resolve a discrepancy existing in the literature between structural models proposed on the basis of experimental data and theoretically derived models. Also, the working hypothesis that the B_Si-Si_i defect is the cause of the so-called boron-oxygen-light-induced degradation (BO-LID) will be checked. For this purpose, the structure and kinetics of the defect shall be analyzed experimentally and simultaneously described theoretically. For example, calculated barrier heights between two states of this defect shall be compared with the results of three different experimental methods. These are low-temperature photoluminescence spectroscopy, electron spin resonance spectroscopy, and microwave-detected photoconductivity decay for carrier lifetime measurement. Annealings of various silicon samples are carried out with the aim of controlling the defect in a controlled manner. For this purpose, the samples are first prepared with the highest possible defect density, and therefore strong signals are to be expected. Targeted anneal protocols aim to achieve a sustained reduction in defect density. From a technological perspective, this can be used to counteract the problem of loss of efficiency due to irradiation. The main goal of the research project, however, is to develop a fundamental and comprehensive microscopic understanding of and a model for the A_Si-Si_i defect, its structure and dynamics as well as the defect-induced recombination of charge carriers.