Open-circuit voltage photodetector architecture for infrared imagers
Abstract
We theoretically and experimentally investigate the application of an open-circuit voltage photodetector (VocP) architecture for mid-wave infrared (MWIR, 3–5 μm) detection and imaging. In contrast to conventional reverse-bias (RB) operation of the diode, which generates a photocurrent that is proportional to the photon irradiance, we evaluate the potential of using unbiased diodes that generate an open-circuit voltage, VOC, under illumination. The predicted Noise Equivalent Differential Temperature (NEDT) of a VocP is inferior to conventional RB when we assume an infinite well capacity and fixed integration time, but the prediction reverses when the actual well capacity of a readout integrated circuit (ROIC) is taken into account. Therefore, for a focal plane array (FPA) with a ROIC, we predict superior NEDT for the VocP. To demonstrate this concept, we fabricated and tested a basic VocP unit-cell architecture by connecting the VOC anode of a MWIR photodiode to the gate of an n-type metal-oxide semiconductor transistor that is operated in sub-threshold. Very good agreement is obtained between the analytical model and the observed drain current of the transistor over three orders of photon irradiance (1015–1018 photons/sec-cm2). The decoupling of the diode photocurrent from the integration capacitor in the circuit leads to a lower dark current that allows for longer integration times and improved sensitivity. This potentially can have a great impact on the performance and functionality of FPAs, leading to FPAs with better NEDT at a higher operating temperature, wider dynamic range, and smaller pixel size leading to larger array formats.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 19, 2020
- Source ID
- 10.1063/5.0020000
Entities
People
- C. Reyner
- Douglas Smith
- Elliot J. Fuller
- Gamini Ariyawansa
- Joshua M. Duran
- Ramy Tantawy
- Roman Fragasse
- Sanjay Krishna
- T. R. Specht
- Theodore J. Ronningen
- Waleed Khalil
- Zahra Taghipour
Organizations
- Air Force Research Laboratory
- Defense Advanced Research Projects Agency
- Ohio State University