Large area single and stacked p-i-n photodiodes as a color image sensors

摘要

Single and stacked p-i-n sensing elements for image recognition and color extraction applications are presented. The aim of this work is to optimize the performance of the a-SiC:H thin films layers in order to enhance its performance when making part of the structure of large area image and color sensors. The efforts are focused mainly on doped n- and p-type layers at high and low doping levels with and without carbon. The structural and optoelectronic properties of the single layers were determined through infrared and visible spectroscopy, temperature-dependent conductivity, and were complemented by CPM measurements. Junction properties, carrier transport, photogeneration and collection efficiency are investigated from dark and illuminated current-voltage characteristics and spectral response measurements, with and without additional background illumination and under different light bias conditions. The spectral response dependence on the applied voltage and on optical bias was also studied. Results show that the spectral sensitivity is strongly dependent on the applied voltage, namely the maximum spectral sensitivity shifts with the voltage, and at certain wavelengths the spectral response goes down to zero, which allows a different selectivity, and enables color recognition.