With the next generation observatories such as GMT, TMT, and E-ELT looming, the astronomy community is in need of unprecedented number of infrared pixels. To address the affordability of the next generation of infrared instruments, the Center for Detectors (CfD) at the Rochester Institute of Technology (RIT) and Raytheon Vision Systems (RVS) are developing large format, short-wave infrared HgCdTe focal plane arrays grown on silicon (Si) wafers for observational astronomy. The use of silicon wafers offers significant savings and a path to very large format (>; 8K×8K, 15 μm) focal plane arrays. This paper presents the latest results from the detector development effort and its suitability for use in observational astronomy. Currently, the HgCdTe/Si technology is competitive with the state-of-the-art HgCdTe/CZT technology in many performance metrics, and it has the promise to meet stringent performance requirements posed by observational astronomy. A full suite of characterization results, including for dark current, read noise, spectral response, persistence, linearity, full well, and crosstalk probability, will be presented.
Radiation testing results for a Geiger-mode avalanche photodiode (GM-APD) array-based imager are reviewed. Radiation testing is a crucial step in technology development that assesses the readiness of a specific device or instrument for space-based missions or other missions in high-radiation environments. Pre- and postradiation values for breakdown voltage, dark count rate (DCR), after pulsing probability, photon detection efficiency (PDE), crosstalk probability, and intrapixel sensitivity are presented. Details of the radiation testing setup and experiment are provided. The devices were exposed to a total dose of 50 krad(Si) at the Massachusetts General Hospital’s Francis H. Burr Proton Therapy Center, using monoenergetic 60 MeV protons as the radiation source. This radiation dose is equivalent to radiation absorbed over 10 solar cycles at an L2 orbit with 1-cm aluminum shielding. The DCR increased by 2.3 e−/s/pix/krad(Si) at 160 K, the afterpulsing probability increased at all temperatures and settings by a factor of ∼2, and the effective breakdown voltage shifted by +1.5 V. PDE, crosstalk probability, and intrapixel sensitivity were unchanged by radiation damage. The performance of the GM-APD imaging array is compared to the performance of the CCD on board the ASCA satellite with a similar radiation shield and radiation environment.
The Center for Detectors at Rochester Institute of Technology and Raytheon Vision Systems (RVS) are leveraging RVS capabilities to produce large format, short-wave infrared HgCdTe focal plane arrays on silicon (Si) substrate wafers. Molecular beam epitaxial (MBE) grown HgCdTe on Si can reduce detector fabrication costs dramatically, while keeping performance competitive with HgCdTe grown on CdZnTe. Reduction in detector costs will alleviate a dominant expense for observational astrophysics telescopes. This paper presents the characterization of 2.5μm cutoff MBE HgCdTe/Si detectors including pre- and post-thinning performance. Detector characteristics presented include dark current, read noise, spectral response, persistence, linearity, crosstalk probability, and analysis of material defects.
The ability to count single photons is necessary to achieve many important science objectives in the near future. This paper presents the lab-tested performance of a photon-counting array-based Geiger-mode avalanche photodiode (GMAPD) device in the context of low-light-level imaging. Testing results include dark count rate, afterpulsing probability, intra-pixel sensitivity, and photon detection efficiency, and the effects of radiation damage on detector performance. The GM-APD detector is compared to the state-of-the-art performance of other established detectors using Signal-to-noise ratio as the overall evaluation metric.
Single-photon imaging detectors promise the ultimate in sensitivity by eliminating read noise. These devices could
provide extraordinary benefits for photon-starved applications, e.g., imaging exoplanets, fast wavefront sensing, and
probing the human body through transluminescence. Recent implementations are often in the form of sparse arrays that
have less-than-unity fill factor. For imaging, fill factor is typically enhanced by using microlenses, at the expense of
photometric and spatial information loss near the edges and corners of the pixels. Other challenges include afterpulsing
and the potential for photon self-retriggering. Both effects produce spurious signal that can degrade the signal-to-noise
ratio. This paper reviews development and potential application of single-photon-counting detectors, including highlights
of initiatives in the Center for Detectors at the Rochester Institute of Technology and MIT Lincoln Laboratory.
Current projects include single-photon-counting imaging detectors for the Thirty Meter Telescope, a future NASA
terrestrial exoplanet mission, and imaging LIDAR detectors for planetary and Earth science space missions.
This paper summarizes progress of a project to develop and advance the maturity of photon-counting detectors for
NASA exoplanet missions. The project, funded by NASA ROSES TDEM program, uses a 256×256 pixel silicon Geigermode
avalanche photodiode (GM-APD) array, bump-bonded to a silicon readout circuit. Each pixel independently
registers the arrival of a photon and can be reset and ready for another photon within 100 ns. The pixel has built-in
circuitry for counting photo-generated events. The readout circuit is multiplexed to read out the photon arrival events.
The signal chain is inherently digital, allowing for noiseless transmission over long distances. The detector always
operates in photon counting mode and is thus not susceptible to excess noise factor that afflicts other technologies. The
architecture should be able to operate with shot-noise-limited performance up to extremely high flux levels,
>106 photons/second/pixel, and deliver maximum signal-to-noise ratios on the order of thousands for higher fluxes. Its
performance is expected to be maintained at a high level throughout mission lifetime in the presence of the expected