Thin-film phototransistor with nc-Si: H/a-Si:H bilayer channel

Y. Vygranenko, A. Sazonov, M. Fernandes, M. Vieira, A. Nathan

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


There is significant interest in optical sensors whose fabrication process is fully compatible with existing flat panel display thin film transistor (TFT) technology. Here, we report a field-effect phototransistor with a channel comprising a thin nanocrystalline silicon (nc-Si:H) transport layer and a thicker hydrogenated amorphous silicon (a-Si:H) absorption layer. The implementation of nc-Si:H layer improves device stability in comparison with a-Si:H phototransistors, resulting in reduced threshold voltage shift. Semiconductor and dielectric layers were deposited by radio-frequency plasma enhanced chemical vapor deposition at 280°C. The device characterization included the dark and light transfer characteristics, spectral-response and dynamic measurements. The external quantum efficiency was measured as a function of incident photon flux at different biasing conditions. The phototransistor with channel length of 24 microns and photosensitive area of 1.4 mm2 shows an off-current of about 1 pA, and photoconductive gain up to 200 at low incident intensities. Thus, the results demonstrate the feasibility of the phototransistor for low light level detection.

Original languageEnglish
Title of host publicationAmorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2012
Number of pages6
Publication statusPublished - 28 Nov 2012
Event2012 MRS Spring Meeting - San Francisco, CA, United States
Duration: 9 Apr 201213 Apr 2012


Conference2012 MRS Spring Meeting
Country/TerritoryUnited States
CitySan Francisco, CA


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