Novel approach to improve reliable color recognition in a-Si:H photodiodes

Krystian Watty; Andreas Bablich; Konstantin Seibel; Christian Merfort; Markus Böhm

doi:10.1117/12.918566

Translator Disclaimer

19 May 2012 Novel approach to improve reliable color recognition in a-Si:H photodiodes

Krystian Watty, Andreas Bablich, Konstantin Seibel, Christian Merfort, Markus Böhm

Author Affiliations +

Proceedings Volume 8376, Photonic Microdevices/Microstructures for Sensing IV; 83760N (2012) https://doi.org/10.1117/12.918566
Event: SPIE Defense, Security, and Sensing, 2012, Baltimore, Maryland, United States

Abstract

Optical detection is an often used technique for recognition of potentially dangerous materials. Hydrogenated amorphous silicon (a-Si:H) technology provides an inexpensive alternative material compared to crystalline silicon for being used in photonic devices operating in the visible spectrum. Further materials' key benefits are the high light absorption, the voltage-tunable spectral sensitivity and the high space efficiency. Present research efforts concentrate on the determination of the color information in a-Si:H photodiodes. This work presents an approach to improve color recognition of a-Si:H photodiodes by modifying the layer sequence. The maximum of the spectral response (SR) of a single i-layer a-Si:H photodiode can be shifted by varying its bias voltage. In this case, the shift is not more than some nanometers. Precise color recognition requires different SR maxima (e.g. RGB-model). One possibility to accomplish a separation of the SR is to engineer the bandgap; another idea, which is presented here, is based on a layer sequence modification. Normally, the SR at higher reverse bias voltages, with the maximum at longer wavelengths, encloses that at lower voltages. Splitting the SR leads to an improvement of color recognition and is achieved by depositing an additional interior anode. The SR maximum shift amounts to 100nm, from 570nm by contacting the interior anode, to 670nm at the top anode. Furthermore, the curves are clearly split. The presented approach should lead to a tunable multi-spectral photodiode for high quality color recognition. Such a diode can be used in photonic devices, e.g. for safety and security applications.

Citation Download Citation

Krystian Watty, Andreas Bablich, Konstantin Seibel, Christian Merfort, and Markus Böhm "Novel approach to improve reliable color recognition in a-Si:H photodiodes", Proc. SPIE 8376, Photonic Microdevices/Microstructures for Sensing IV, 83760N (19 May 2012); https://doi.org/10.1117/12.918566

ACCESS THE FULL ARTICLE