Thin-Film Color Sensor Arrays
- PDF / 121,930 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 42 Downloads / 217 Views
THIN-FILM COLOR SENSOR ARRAYS D. Knippa,c, R.A. Streeta, H. Stiebigb, M. Krauseb,d, J.-P Lua, S. Readya, J. Hoa, a.) Palo Alto Research Center, Electronic Materials Laboratory, Palo Alto, CA 94304 b.) Research Center Jülich, Institute of Photovoltaics, 52425 Jülich, Germany c.) International University Bremen, Department of Science and Engineering, 28759 Bremen, Germany d.) now with Infineon Technology, Dresden, Germany ABSTRACT Color information is commonly captured by silicon sensor arrays covered by a mosaic of color filters. However, the detection of the colors red, green and blue at different spatial positions of the sensor arrays leads to color aliasing or color moiré effects. This effect inherently limits conventional sensor arrays. In order to overcome this limitation we have realized color sensors based on vertically integrated thin-film structures. The complete color information can be detected at the same position of a sensor array without using optical filters. The sensors consist of a multilayer thin-film system based on amorphous silicon and its alloys. The spectral sensitivity of the sensors can be controlled by the optical and optoelectronic properties of the employed materials and the applied bias voltages. The working principle of the thin-film sensors and the sensor arrays will be presented. For the first time a large area three color sensor array was realized without using optical filters. INTRODUCTION Imaging is usually performed by silicon sensor arrays in combination with color filter arrays (CFA). The color filter array is typically realized by a spatial arrangement of at least three types of filters for the colors red, green and blue. Therefore, three chromatic color pixels are required to form a color pixel, which limits the resolution of conventional sensor arrays. Furthermore, color detection using CFAs leads to color moiré or color aliasing effects, which are observed when structures with high spatial frequencies are captured. In order to overcome the color moiré effect, vertically integrated sensors have been proposed, which detect the color information in the depth of the sensor structure. Due to the wavelength dependent absorption of the semiconductor material, photons are absorbed at various depths, so that the color information can be detected in the depth of the device. Various sensor structures have been realized by using different materials, design concepts and contact configurations [1-9]. The suggested sensors range from two terminal devices, which change their spectral sensitivity by varying the applied bias voltage to vertically stacked diodes. So far only the sensor technology developed by Foveon has been commercialized [1]. The sensor structure consists of three vertical integrated pn-junctions fabricated by standard silicon BiCMOS processing. Sensor arrays with a resolution of 10.6Mpixels and metameric errors comparable to CFA based sensor arrays were presented [10]. Even though the color
D1.6.1
D1.6.2
moiré effect is getting more pronounced for larger pixels, the real
Data Loading...
