InGaAs photodiode arrays have been developed to 'cover' the SWIR wavelength range in spectroscopy. Hybridized Si/InGaAs linear arrays have become the detector of choice for remote sensing. Device 'long' wavelength spectral performance is achieved by rearranging the photodiodes In/Ga stoichiometric ratio. However, increased long wavelength response adversely affects deice characteristics. The self-scanned InGaAs linear array mechanical and opto/electronic properties will be discussed.
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.
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