Project Details
Projekt
Calculation, measurement and control of the energy barriers and the light-induced kinetics of the A_Si-Si_i defect
Subject Area
Experimental Condensed Matter Physics
Term
since 2020
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 445152322
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.
DFG Programme
Research Grants
Co-Investigators
Dr. Anna Dimitrova; Privatdozent Dr. Rüdiger Schmidt-Grund; Dr. Dirk Schulze
