Stacked amorphous silicon color sensors

Abstract

Abstract-Color sensors based on vertically integrated thin-film structures of amorphous silicon ( -Si : H) and its alloys were realized to overcome color moiré or color aliasing effects. The complete color information of the color aliasing free sensors is detected at the same spatial position without the application of additional optical filters. The color separation is realized in the depth of the structure due to the strong wavelength dependent absorption of -Si : H alloys in the visible range. The sensors consist of three stacked p-i-n diodes. The spectral sensitivity of the sensors can be controlled by the optical and electronic properties of the materials on one hand and the design of the devices on the other hand. In order to investigate the optical wave propagation within the device and to optimize the color separation we have developed an optical model, which takes the optical properties of the individual layers and the device design into account. The optical model has been combined with a colorimetric model, which facilitates the benchmarking of the color sensors and the reduction of the color error of the sensors. Finally, an improved device design will be presented.

Organic Photodiodes: The Future of Full Color Detection and Image Sensing

“…Pixelated Multilayer (Stacked) OPD Color Imaging : As previously discussed, Higashi et al and Lamprecht et al introduced extra layers into the OPD devices to absorb wavelengths outside the desired spectral window to give a narrower response. An extension of the concept is to make multilayer (stacked) OPD sensors for imaging, which is a similar approach to that used in the Foveon X3 [ 42 ] ( Figure 18 a), with the work largely built on the seminal work by Tang. [ 249 ] NHK (Nippon Hoso Kyokai -the Japan Broadcasting Corporation [ 250 ] ) have worked extensively on developing this concept.…”

“…The approach is based on the fact that red, green, and blue light penetrate silicon to different depths, [ 42 ] thereby enabling an image sensor that essentially captures light of each of the colors in every pixel. The approach obviates the need for color fi lters and maximises light utilization and sensitivity.…”

“…Crystalline silicon has high carrier mobilities with long lifetimes that can lead to crosstalk between neighboring pixels. [ 38 ] In terms of REVIEW the optical properties, both amorphous and crystalline silicon absorb light broadly over the visible spectrum, meaning that it is diffi cult to achieve color discrimination with the material alone, and the absorption is relatively weak, [ 33,36 ] particularly in the violet-blue region (400-460 nm), [ 42,43 ] thus requiring the use of relatively thick photoactive junctions. Furthermore, the fact that silicon has a smaller band-gap than required for visible detection (the band-gap of Si is ≈1.1 eV at 300 K [39]) means that infrared (IR) fi lters are required in order to avoid unwanted IR sensitivity.…”

Evanescent Waveguide Sensor for On-Chip Biomolecular Detection

“…The optoelectronic characteristics of the a-Si:H make this material one of the most promising for the fabrication of thin film devices both in large area electronics [15] and in sensor applications [16,17]. In particular, the low deposition temperature of a-Si:H (below 250 °C) allows the use of different substrates, making it a valuable material for biomolecular recognition applications in compact integrated systems, with performances comparable to those of the c-Si photodiodes [18].…”

Biomimetic Radial Tandem Junction Photodetector with Natural RGB Color Discrimination Capability

“…In this work, we propose a novel 3D radial tandem junction (RTJ) photodetector design, consisting of two radially stacking hydrogenated amorphous silicon (a‐Si:H) PIN junctions over 3D silicon nanowire (SiNW) cores as schematically illustrated in Figure b, to achieve natural RGB‐color‐discrimination in the RTJ rod‐cells without the need of any filter system. It is important to note, the a‐Si:H layer allows a much stronger light absorption compared to that of c‐Si, with an order of magnitude stronger light absorption coefficient over the full human vision spectrum, as shown in Figure d. Built over a 3D NW framework, a highly efficient light trapping and absorption can be expected thanks to the unique resonant‐mode‐assisted wavelength‐selective absorption profile within the cavity‐like nanowire radial junction units .…”