Optoelectronic characterization of a-SIC:H stacked devices

Abstract

The aim of this work is the optoelectronic characterization of double p–i–n stacked devices based on a-Si alloy materials, in order to evaluate their suitability in large area optical sensors. Photogeneration, collection efficiency and carrier transport are investigated from dark and illuminated current–voltage characteristics and spectral response measurements, with and without additional background illumination and different electrical bias conditions. Results show that the collection efficiency depends on the device configuration and on the optical and electrical bias. The carrier collection is mainly dependent on the front and back intrinsic layers thickness and on the composition of the p-type doped layers. When wide band gap p-layers are used, the asymmetric distribution of the electrical field controls the transport mechanism. Under red optical bias the electrical field is enhanced at the front cell and decreased at the back one leading to an increased red light-to dark sensitivity. A numerical simulation supports the discussion of the experimental results. Considerations about induced electric field and inversion layers at the interfaces and generationrecombination process are used to explain the device output.