Defect Engineering (DFG)
| Project name: | Advanced defect engineering and surface passivation for improving the carrier lifetime in femtosecond laser sulfur hyperdoped silicon |
| Department: | Engineering – Applied Physics |
| Project lead: | Prof. Dr. rer. nat. Stefan Kontermann |
| Project partners: | Georg-August University of Göttingen |
| Duration: | 01.11.2020 – 30.09.2024 |
| Funding body or client: | German Research Foundation (DFG), grant number 429413061 |
Project description
Irradiating silicon with ultrashort laser pulses in a sulfur hexafluoride atmosphere results in sulfur hyperdoping of the silicon. The sulfur doping allows photons with long wavelengths to be absorbed, which enables the use of hyperdoped silicon in infrared detectors and photovoltaics. However, the laser process also damages the crystalline structure of the silicon, which strongly reduces the carrier lifetime.
Objective
The project investigates the correlation between macroscopic and microscopic material properties of femtosecond-laser sulfur-hyperdoped silicon and relates them to the process parameters:
- Macroscopic: external and internal quantum efficiency and carrier lifetime
- Microscopic: excess carrier recombination (electron beam induced current, EBIC), deep defect states (deep level transient spectroscopy, DLTS), the surface (atomic force and Kelvin probe microscopy, AFM and KPFM) and the underlying hyperdoped region (scanning and transmission electron microscopy, SEM and TEM)
The aim is to identify and specifically modify application-relevant defect formation and defect reactions. In addition to a deeper understanding of the material, optimal process parameters as well as a tailored post-treatment and passivation are developed to maximise the carrier lifetime.
Project partners and tasks
- RheinMain University of Applied Sciences, Rüsselsheim: fabrication of femtosecond-laser sulfur-hyperdoped silicon, increasing the carrier lifetime by passivation with dielectric layers, defect engineering of sulfur impurities through various post-treatment methods and adjustment of the process parameters, defect engineering through femtosecond pulse overlap
- University of Göttingen: investigation of the microscopic, macroscopic and surface-morphological properties, correlation of the measurement results
Funding
The project is funded by the German Research Foundation (DFG). The DFG serves science in all its branches by funding research projects and promoting national and international cooperation among researchers, with particular attention to supporting early-career researchers.
