We present the results of a radiation test program for a 1-megapixel single-photon-counting and photon-number-resolving CMOS image sensor. The results include pre- and post-radiation values for dark current, voltage shift at the pixels’ output, read noise, quantum efficiency (QE), conversion gain, and photon counting ability. The Center for Detectors at the Rochester Institute of Technology exposed the sensor to a 50-krad(Si) dose of 60-MeV protons, equivalent to the dose absorbed over 10 11-year space missions at L2 with 1-cm aluminum shielding. The median dark current of the sensor increased from 0.00085 to 0.0085 e−/s/pix at 258 K and from 0.0075 to 0.075 e−/s/pix at 282 K. This is an increase of 2.0 fA/cm2/krad(Si) and 17.8 fA/cm2/krad(Si), respectively. Performance in other metrics remained constant: 0.34 e− median read noise, 85% peak QE at 490 nm, and photon number resolution. We report mostly total ionizing dose and displacement damage dose effects and compare the radiation tolerance of the device to the performance of state-of-the-art charge coupled devices and CMOS devices. The detector exhibits a comparable radiation tolerance to the expected tolerance of modern CMOS devices.
NASA seeks to identify habitable exoplanets and explore signatures of life with the Habitable Worlds Observatory and through a series of missions to Europa. The former requires single photon sensing detectors that measure fluxes as low as one photon per hour, while the latter requires detectors that maintain performance after exposure to intense high-energy space radiation. Single-photon sensing and photon-number resolving CMOS image sensors are promising for these missions. One such sensor, the Quanta Image Sensor (QIS), has deep sub-electron read noise (DSERN) that remains unchanged even after exposure equivalent to that experienced over ten 11-year mission lifetimes. The dark current increases modestly after one mission lifetime and can be returned to beginning-of-life values with cooling of ~4 to 6K. In this paper, we present pre-irradiation results obtained from another DSERN sensor, the BAE HWK4123 in the Hamamatsu ORCA-QUEST camera. We find the read noise, photon transfer, and full well depth agree with reported values for the camera, while the dark current is 2.8× higher than the reported value. We also present a radiation test program plan, including simulations of the environment at L2 and around Jupiter.
High-performance large-format infrared (IR) detectors for astronomy will be in high demand for the next generation of ground- and space-based IR observatories. We present advances in previously published characterization results of HgCdTe-on-Silicon (MCT/Si) IR detectors developed by the RIT Center for Detectors (CfD) and Raytheon Vision Systems (RVS) through the SWIR Advanced Technology Instruments for NSF and NASA (SATIN) development program. The program successfully demonstrates the feasibility of MCT/Si detectors as a competitive architecture for astronomy applications, and we believe that future MCT/Si detectors will lower the cost of IR focal plane arrays by approximately a factor of five. We analyze the correlation between p-n junction size and quantum efficiency and full well depth, and present initial results from an observing program carried out with the best detector of the SATIN project. Finally, we outline a plan to conduct proton and heavy ion radiation testing of the devices to evaluate the radiation tolerance of the MCT/Si technology for space-based applications.
The next UV/O/IR flagship observatory mission recommended by the 2020 Decadal Survey on Astronomy and Astrophysics requires detector performance beyond what many devices deliver; i.e., lower dark current, lower read noise, higher QE, photon counting capability, etc. We evaluate how detector performance parameters affect the ability of an instrument to satisfy the science goals described in the LUVOIR concept study. We compare the requirements to performance in relevant metrics for current state-of-the-art devices. Current UV/O devices (specifically photon-counting CMOS ones) already perform at a level that meet most of the requirements of the upcoming flagship mission. We find that CMOS devices provide performance characteristics that exceed the requirements and exist in formats that demonstrate scalability beyond tens of mega-pixels. EMCCDs have demonstrated scalability to this size as well, though the excess noise factor introduced by the gain mechanism presents significant issues. MKIDs can resolve photon energy, but have yet to demonstrate scalability to mega-pixel formats. SNSPDs do not currently have readout architectures beyond the kilo-pixel level.
Single-photon sensing and photon-number resolving image sensors are key to enabling projects that are not possible today. We present detector characterization results for four single-photon sensing and photon-number resolving backside illuminated complementary metal-oxide semiconductor (CMOS) image sensors. Eric R. Fossum and his team at Dartmouth College led early detector development and continues through Gigajot Technology Inc. The CMOS image sensors have pixels (1.1 μm pitch) that use small-capacitance floating diffusions to achieve deep sub-electron read noise (<0.5 e− RMS). Characterization results include dark current, read noise, quantum efficiency, persistence, linearity, well depth. We also report on our ongoing work to use the image sensors for astronomical observations. We compare the performance of the four CMOS image sensors to that of state-of-the-art detectors, particularly with respect to the large UV/O/IR space telescope recommended by the 2020 Decadal Survey on Astronomy and Astrophysics.
We describe progress developing infrared detectors with HgCdTe grown on silicon substrates using Molecular Beam Epitaxial growth. The project is a collaboration between the RIT Center for Detectors and Raytheon Vision Systems (RVS). NASA and NSF jointly funded the program, known as SATIN (Short-wave infrared Advanced Technologies and Instrumentation program funded by NASA and NSF). We present detector characterization results for detectors made in the final lot of devices made by RVS. A full suite of characterization results, including for dark current, read noise, spectral response, persistence, linearity, full well, and crosstalk probability, are presented. The performance satisfies requirements for astronomy imaging applications. We plan to use the design to make HELLSTAR (HgCdTe Extremely Large Layout Sensor Technology for Astrophysics Research), a 4K×6K infrared detector with the highest number of pixels ever made for infrared astronomy.
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