Joseph P. Rosbeck

2Kx2K InSb for astronomy

Raytheon Vision Systems is under contract to develop 2K × 2K InSb Focal Plane Arrays (FPA) for the ORION and NEWFIRM projects teaming with NOAO, NASA, and USNO. This paper reviews the progress in the ORION, NEWFIRM, and the JWST projects, showing bare mux readout noise at 30 K of 2.4 e- and InSb dark current as low as 0.01 e-/s. Several FPAs have been fabricated to date and the ongoing improvements for the fabrication of FPAs will be discussed. The FPA and packaging designs are complete, resulting in a design that has self-aligning features for ease in FPA replacement at position of the focal plane assembly with alignment accuracy in the focus direction of ± 12 μm. The ORION/NEWFIRM modules are 2-side buttable to easily form 4K × 4K mosaics while the Phoenix modules, developed under the JWST development program, are 3-side buttable for ease in forming 4K × 2NK mosaics where N can be any integer. This paper will include FPA QE, dark current and noise performance, FPA reliability, and module-to-module flatness capabilities.

Megapixel InGaAs arrays for low background applications

Large focal planes with InGaAs detector arrays have been developed that meet the demanding requirements of astronomy and other low background systems. With high quantum efficiency between 0.9 and 1.7 μm, the InGaAs detectors are ideally suited for many SWIR applications. This paper describes two types of arrays with more than one million detector elements-one with 1280 × 1024 elements and the other with 1024 × 1024 elements-developed by Raytheon Vision Systems with detectors provided by Sensors Unlimited. The detector elements of both formats are on a 20 μm pitch. The 1024 × 1024 array utilizes a standard Virgo astronomy multiplexer (readout) that reads out the array at a maximum frame rate of 8 Hz. An innovative readout was designed for the 1280 × 1024 array with the support of DARPAs MANTIS program. This readout features a high gain front-end amplifier that can operate up to a 60 Hz frame rate and is designed to operate at room temperature. Summary performance data of each of these array types are presented.

Advances in linear and area HgCdTe APD arrays for eyesafe LADAR sensors

HgCdTe APDs and APD arrays offer unique advantages for high-performance eyesafe LADAR sensors. These include: operation at room temperature, low-excess noise, high gain, high-quantum efficiency at eyesafe wavelengths, GHz bandwidth, and high-packing density. The utility of these benefits for systems are being demonstrated for both linear and area array sensors. Raytheon has fabricated 32 element linear APD arrays utilizing liquid phase epitaxy (LPE), and packaged and integrating these arrays with low-noise amplifiers. Typical better APDs configured as 50-micron square pixels and fabricated utilizing RIE, have demonstrated high fill factors, low crosstalk, excellent uniformity, low dark currents, and noise equivalent power (NEP) from 1-2 nW. Two units have been delivered to NVESD, assembled with range extraction electronics, and integrated into the CELRAP laser radar system. Tests on these sensors in July and October 2000 have demonstrated excellent functionality, detection of 1-cm wires, and range imaging. Work is presently underway under DARPAs 3-D imaging Sensor Program to extend this excellent performance to area arrays. High-density arrays have been fabricated using LPE and molecular beam epitaxy (MBE). HgCdTe APD arrays have been made in 5 X 5, 10 X 10 and larger formats. Initial data shows excellent typical better APD performance with unmultiplied dark current < 10 nA; and NEP < 2.0 nW at a gain of 10.

InSb arrays for IRAC (infrared array camera) on SIRTF (Space Infrared Telescope Facility)

SIRTF requires detector arrays with extremely high sensitivity, limited only by the background irradiance. Especially critical is the near infrared spectral region around 3 micrometers , where the detector current due to the zodiacal background is a minimum. IRAC has two near infrared detector channels centered at 3.6 and 4.5 micrometers . We have developed InSb arrays for these channels that operate with dark currents of < 0.2 e/s and multiply-sampled noise of approximately 7 e at 200 s exposure. With these specifications the zodiacal background limited requirements has been easily met. In addition, the detector quantum efficiency of the InSb devices exceeds 90% over the IRAC wavelength range, they are radiation hard, and they exhibit excellent photometric accuracy and stability. Residual images have been minimized. The Raytheon 256 X 256 InSb arrays incorporate a specially developed (for SIRTF) multiplexer and high-grade InSb material.

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.

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.

Large-format infrared arrays for future space and ground-based astronomy applications

The 1990s saw the rapid evolution of staring IR focal plane arrays (FPAs), with array formats progressing from 128 by 128 arrays at the beginning of the decade, to 1K by 1K arrays in low-rate production at the end of the decade. The maturation of large-format staring FPAs has given astronomers new capabilities for wide-field, high-resolution imaging and spectroscopy. The trends that emerged in the 1990s are continuing with larger format FPAs currently under development.

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.

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.