An improved wide dynamic range silicon photodetector for integration in image sensor arrays

Abstract

DALSA Inc., Waterloo, Ont., has designed, simulated, and tested a novel silicon photodetector offering several important performance advantages over current industry-standard devices. Currently available imaging devices offered by various manufacturers are typically sensitive to varying light intensity over three orders of magnitude in optical power, while DALSA's novel design offers a logarithmic response of greater than six orders of magnitude in light intensity.Designed to use to advantage the subthreshold effect of short-channel metal oxide semiconductor field effect transistors, the new device is readily integrated into large arrays featuring charge coupled device readout shift registers and metal oxide semiconductor support circuitry. Several devices designed by DALSA incorporating the new detector have been fabricated and tested, including discrete detectors, linear arrays, and area arrays.This paper discusses the theory of operation and performance of an improved wide dynamic range photodetector. Performance considerations include dynamic range, quantum efficiency, noise and noise equivalent power, responsivity, and speed. This photodetector can be integrated to form silicon image sensor arrays. Experimental results will also be presented that demonstrate a maximum-to-minimum detectable light intensity of greater than 106.