Ken J. Ando

1Kx1K Si:As IBC detector arrays for JWST MIRI and other applications

1K × 1K Si:As Impurity Band Conduction (IBC) arrays have been developed by Raytheon Vision Systems (RVS) for the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). The devices are also suitable for other low-background applications. The Si:As IBC detectors respond out to ~28 microns, covering an important mid-IR region beyond the 1-5 micron range covered by the JWST NIRCam and NIRSpec instruments. Due to high terrestrial backgrounds at the longer mid-IR wavelengths, it is very difficult to conduct ground-based observations at these wavelengths. Hence, the MIRI instrument on JWST can provide science not obtainable from the ground. A mid-infrared instrument aboard a cryogenic space telescope can have an enormous impact in resolving key questions in astronomy and cosmology. The greatly reduced thermal backgrounds achievable on a space platform (compared to airborne or ground-based platforms) allow for more sensitive observations of dusty young galaxies at high redshifts, star formation of solar-type stars in the local universe, and formation and evolution of planetary disks and systems. We describe results of the development of a new 1024 × 1024 Si:As IBC array with 25-micron pixels that responds with high quantum efficiency over the wavelength range 5 to 28 microns. The previous generations largest, most sensitive IR detectors at these wavelengths were the 256 × 256/30-micron pitch Si:As IBC devices built by Raytheon for the SIRTF/IRAC instrument. JWST MIRI detector requirements will be reviewed and some model results for IBC device performance will be presented. The IBC detector architecture will be described and the SB305 Readout Integrated Circuit (ROIC), developed specifically for JWST MIRI, will be discussed. The SB305 ROIC utilizes a PMOS Source Follower per Detector (SFD) input circuit with a well capacity of about 2 × 105 electrons. The read noise is expected to be less than 20 e- rms with Fowler-8 sampling at an operating temperature of 7 K. Other features of the IBC array include 4 video outputs and a separate reference output with a frame rate of 0.37 Hz (2.7 sec frame time). Power dissipation is less than 0.5 mW at a 0.37 Hz frame rate. Reset modes include both global reset and reset by row (ripple mode). Reference pixels are built-in to the output data stream. The 1K × 1K IBC is packaged in a robust modular package that consists of a multilayer motherboard, silicon carbide (SiC) pedestal, and cable assembly with 51-pin MDM connectors. All materials of construction were chosen to match the thermal expansion coefficient of silicon to provide excellent module thermal cycle reliability for cycling between room temperature and 7 K.

Infrared detectors for ground-based and space-based astronomy applications

This paper will review the state-of-the-art IR detectors at the Raytheon IR Center of Excellence for both grou8nd-based and space-based astronomy applications. Performance data will be presented on 0.5 to 5.0 micron Indium Antimonide (InSb) arrays and 0.9 to 5.0 micron Mercury Cadmium Telluride arrays. In addition, performance data on 2 to 28 micron Arsenic-doped Silicon impurity band conductor arrays will be presented. These very high performance detector array offer another important window into the universe for ground- and space-based astronomical work. Data will include performance data on InSb and Si:As IBC arrays for the IR array camera instrument on NASAs Space IR Telescope Facility and the IRC instrument on the ISAS ASTRO-F IR Imaging Survey (IRIS) mission. Data obtained with the HgCdTe arrays developed for the Visible and IR Thermal Imaging Spectrometer H and M instruments for the ESA ROSETTA mission will also be presented. Readouts for both ground-based and space-based astronomy applications will be highlighted, including the first prototype multiplexer and 4 K X 4 K Focal Plane Array for the next generation space telescope.

Large-format 0.85- and 2.5-μm HgCdTe detector arrays for low-background applications

The demand for large-format NIR arrays has grown for both ground-based and space-based applications. These arrays are required for maintaining high resolution over very large fields of view for survey work. We describe results of the development of a new 2048 x 2048 HgCdTe/CdZnTe array with 20-micron pixels that responds with high quantum efficiency over the wavelength range 0.85 to 2.5 microns. With a single-layer anti-reflection (AR) coating, the responsive quantum efficiency is expected to be greater than 85% from 0.9 micron to 2.4 microns. The modular package for this array, dubbed the VIRGO array, allows three-side butting to form large mosaic arrays of 4K x 2nK format. The VIRGO readout integrated circuit (ROIC) utilizes a Source Follower per Detector (SFD) input circuit with a well capacity of about 2 x 105 electrons and with a read noise of less than 20 e-rms with off-chip Correlated Double Sampling (CDS). Other features of the VIRGO array include 4 or 16 outputs (programmable), and a frame rate of up to 1.5 Hz in 16-output mode. Power dissipation is about 7 mW at a 1 Hz frame rate. Reset modes include both global reset and reset by row (ripple mode). Reference pixels are built-in to the output data stream. The first major application of the VIRGO array will be for VISTA, the United Kingdom’s Visible and Infrared Survey Telescope for Astronomy. The VISTA FPA will operate near 80K. Dark current is less than 0.1e-/sec at 80K. The cutoff wavelength of the HgCdTe detector can be adjusted for other applications. Space applications might include SNAP, the Supernova/Acceleration Probe, which requires a shorter detector cutoff wavelength of about 1.7 microns. For applications which require both visible and NIR response, the detector CdZnTe substrate can be removed after hybridization, allowing the thinned detector to respond to visible wavelengths as short as 0.4 microns.

Development of Si:As impurity band conduction (IBC) detectors for mid-infrared applications

Si:As Impurity Band Conduction (IBC) detectors offer many significant advantages over other conventional photon detectors utilized for the infrared. SiAs offer excellent spectral response out to 28 μm with dark current in the 0.01e/second range at 7K over a wide bias range with no tunneling limitations. In addition, because of the perfect thermal match between the Si:As IBC detector and the readout IC (ROIC), hybrids formed by mating Si:As IBCs and ROICs are mechanically stable and have no hybrid reliability problems. Since Si:As IBC detectore are fabricated on readily available Si substrates, large formats are realizable. Si:As IBC detectors have been under development since the mid 80s at Raytheon Vision Systems (RVS). Under the NSAS SIRTF program, a 256 x 256 Si:As array was developed and successfully integrated into the SIRTF IRAC instrument. This same array is also utilized in the ASTRO-F IRC instrument. Both missions will be launched shortly and provide a significant improvement in our ability to measure the spectral signatures of solar type stars and galaxies at high redshifts under very low background conditions in space. Under the NASA Origins program, in collaboration with NASA Ames Research Center (ARC), RVS developed a high performance 1024 x 1024 Si:As IBC array. This array was tested at Ames Research Center. This paper will review the progress of Si:As IBC development at RVS, present test data from ARC, and discuss the more recent developments in Si:As IBC detectors for the JWST MIRI instrument and future missions such as SPICA, TPF, FIRST and DARWIN.

Near-IR arrays for ground-based and space-based astronomy

This paper is a review of current astronomy projects at Raytheon/SBRC in the near-IR band. Another paper in this same session (3354-11) covers astronomy projects in longer wavelengths. For ground-based astronomy, InSb arrays with formats of 256 X 256, 512 X 512, and 1024 X 1024 have been developed and tested. For space-based astronomy, four projects are discussed with array formats ranging from 256 X 256 to 2K X 2K. The space projects support instruments on the SIRTF, IRIS, NGST, and Rosetta missions. Representative data are presented from 1024 X 1024 and 256 X 256 arrays obtained by test facilities at NOAO and the University of Rochester.

2Kx2K HgCdTe detector arrays for VISTA and other applications

The demand for large-format near infrared arrays has grown for both ground-based and space-based applications. These arrays are required for maintaining high resolution over very large fields of view for survey work. We describe results of the development of a new 2048 × 2048 HgCdTe/CdZnTe array with 20-micron pixels that responds with high quantum efficiency over the wavelength range 0.85 to 2.5 microns. With a single-layer anti-reflection coating, the responsive quantum efficiency is greater than 70% from 0.9 micron to 2.4 microns. Dark current is typically less than 4 e-/sec at 80 K. The modular package for this array, dubbed the VIRGO array, allows 3-side butting to form larger mosaic arrays of 4K × 2nK format. The VIRGO ROIC utilizes a PMOS Source Follower per Detector input circuit with a well capacity of about 2 × 105 electrons and with a read noise of less than 20 e- rms with off-chip Correlated Double Sampling. Other features of the VIRGO array include 4 or 16 outputs (programmable), and a frame rate of up to 1.5 Hz in 16-output mode. Power dissipation is about 7 mW at a 1 Hz frame rate. Reset modes include both global reset and reset by row (ripple mode). Reference pixels are built-in to the output data stream. The first major application of the VIRGO array will be for VISTA, the United Kingdom’s Visible and Infrared Survey Telescope for Astronomy. The VISTA focal plane array will operate near 80 K. The cutoff wavelength of the HgCdTe detector can be adjusted for other applications such as SNAP, the Supernova/Acceleration Probe, which requires a shorter detector cutoff wavelength of about 1.7 microns. For applications which require both visible and near infrared response, the detector CdZnTe substrate can be removed after hybridization, allowing the thinned detector to respond to visible wavelengths as short as 0.4 microns.

Megapixel and larger readouts and FPAs for visible and infrared astronomy

The desire for larger and larger format arrays for astronomical observatories -- both ground and space based -- has fueled the development of detector, readout, and hybrid Focal Plane Array (FPA) technology that has paved the way for later development of tactical and strategic arrays for military applications. Since 1994, Raytheon has produced megapixel readouts and FPAs for Infrared Astronomy. In 1999 Raytheon demonstrated a revolutionary approach to photolithography called Reticle Image Composition Lithography (RICL) that opened the door to very large format FPAs in state of the art sub-micron CMOS processes. The first readout processed using the patented RICL technique was a 4.2 megapixel readout for astronomy. We present the design and performance of several 4.2 megapixel (2048 x 2048) readout arrays for visible and infrared astronomy applications. The first of these arrays are fabricated in a workhorse 2 μm CMOS process that is optimized for low temperature operation (down to as low as 6 Kelvin). Most recently Raytheon has developed a scaleable 2,048 x 2,048 high density array for several ground based astronomical applications. This array can be manufactured in any m x n multiple of a basic 1024 (V) x 512 (H) pixel array core. The primary design is a 2 x 4 array to yield a 2,048 x 2,048 format array. This same design can be extended to at least a 4,096 x 4,096 format array -- an incredible 16.7 megapixel array! These readouts are compatible with a wide range of detector types including InSb, HgCdTe, and Si detectors. The use of hybrid technology -- even for the visible wavebands -- allows 100% optical fill factors to be achieved. The design and performance of these megapixel class detectors, readouts, and FPAs will be presented.

Development of 2k x 2k FPA InSb modules for the NGST mission

Raytheon Infrared Operations is under contract to develop 2K x 2K InSb arrays for the NGST NIRcam instrument and 1K x 1K Si:As IBC arrays for the NGST MIRI instrument. This paper reviews the progress in the NIR, showing NGST bare mux readout noise at 30 K of 2.4 e- and InSb dark current as low as 0.02 e-/s. Detectors and readouts have been fabricated in the 2K x 2K format and, except for adding indium bumps to the readouts, are ready for hybridization. Module and FPA designs are complete, resulting in a design that has self-aligning, interchangeable modules and requires no additional cold electronics to perform the NGST mission. Analysis predicts an alignment accuracy in the focus direction of ± 12 μm and total power for a 4K x 4K focal plane of 5 mW.

Overview of Astronomy Arrays at Raytheon Infrared Operations (RIO)

We review the various types of astronomy arrays currently available from RIO for wide-field imaging and spectroscopy. Arrays for infrared astronomy became available from RIO (previously the Santa Barbara Research Center) with the introduction of the 58×62 InSb in 1984. Since the introduction of this first array, RIO has developed and produced increasingly larger format arrays, including the 256×256 InSb array for SIRTF (Space Infrared Telescope Facility) and the Aladdin 1K×1K array. Over 70 Aladdin arrays have been delivered and are currently deployed on a number of major telescopes throughout the world. RIO is currently developing the next generation of 2K×2K format arrays. These include the 2K×2K ORION InSb array, and the VIRGO 2K×K SWIR HgCdTe array for ground-based applications and the 2K×2K InSb array for the NGST program. In addition, RIO is currently developing the next generation large format 1K×1K Si:As Impurity Band Conduction (IBC) arrays for the NGST MIR instrument.

270 x 436 HgCdTe FPA module for the Rosetta VIRTIS-H and -M instruments

This paper will describe a 270 X 436 HgCdTe FPA/module that was developed for the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) H and M instruments. Raytheon Infrared Operations was selected by Officine Galileo and the Observatorie de Paris, Meudon to design, fabricate and deliver 4 flight modules for the VIRTIS H and M spectrometers.