Further developments on a novel color sensitive CMOS detector

Abstract

The Transverse Field Detector (TFD) is a recently proposed Silicon pixel device designed to perform color imaging without the use of color filters. The color detection principle is based on the dependence of the Silicon absorption coefficient from the wavelength and relies on the generation of a suitable transverse electric field configuration, within the semiconductor active layer, to drive photocarriers generated at different depths towards different collecting electrodes. Each electrode has in this way a different spectral response with respect to the incoming wavelength. Pixels with three or four different spectral responses can be implemented within ~ 6 μm of pixel dimension. Thanks to the compatibility with standard triple well CMOS processes, the TFD can be used in an Active Pixel Sensor exploiting a dedicated readout topology, based on a single transistor charge amplifier. The overall APS electronics includes five transistors (5T) and a feedback capacitance, with a resulting overall fill factor around 50%. In this work the three colors and four colors TFD pixel simulations and implementations in a 90 nm standard CMOS triple well technology are described. Details on the design of a TFD APS mini matrix are provided and preliminary experimental results on four colors pixels are presented.