In the PoRr project, a special light sensor was developed that works particularly precisely and minimizes interfering light reflections. A special surface structure changes the reflection behavior and enables the construction of detector assemblies with a light trap. These have significantly improved characteristic values compared to assemblies without surface structuring. The optimized light traps show a higher overall sensitivity with a simultaneous reduction in back reflection of around 15%.
One focus was on the development of a technologically compatible process for creating a micro-textured surface that acts as a light trap and, in addition to the desired optical properties, also allows further processing into active photodiodes. To this end, various wet-chemical and plasma-supported etching processes were tested and used to process treated silicon wafer surfaces into photodiodes. In addition to the desired reduction in reflection, the photodiodes produced show increased sensitivity in the visual spectral range compared to unstructured photodiodes.
Specially developed measuring stations make it possible to record the proportions of the total reflection (specular and diffuse) at different wavelengths and to record the angular distribution of the reflected light at different angles of incidence (azimuth and inclination). The mechanical design and the realized control with user interface enable reproducible measurements of samples with different angular resolutions.
The research and development work described was funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK) as part of the “Photodiodes without back reflection” (PoRr) research project.
Funding code: 49MF210111
