Monolithic active pixel InGaAs focal plane arrays for near-infrared imaging

We present the preliminary results of our investigation into the demonstration of a 16 X 16 element 'active-pixel sensor' array for imaging in the 0.5-2.5 micrometers wavelength spectrum. Each pixel consists of an InGaAs photodiode integrated with InP JFET-based signal processing electronics. An InP-based reset switch in each pixel is addressable using peripheral row and column select switches. The pixel architecture is based on a source-follower circuit. Each pixel has only four devices - three JFETs and a photodetector. This architecture can potentially lead to pixel fill factors in excess of 60 percent. The InP-based JFETs have extremely low leakage currents and high ON/OFF switching ratios. Each photodiode is independently addressed by applying a voltage to the reset terminal. Once the reset transistor Qa is switched ON, the photocurrent drives the output terminal using the source-follower circuit. The Sorce Follower Array architecture facilitates monolithic integration of the InP JFETs and InGaAs photodetectors with up to 2.5micrometers -wavelength cut-off. One important aspect of the JFET design is the p-type InP epilayer under the channel region of the JFET. This grown in p-n junction isolates the channel from the substrate thereby reducing the leakage current of the JFET.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.