Roger S. Holcombe

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.

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.

1024 x 1024 Si:As IBC detector arrays for mid-IR astronomy

1K x 1K Si:As Impurity Band Conduction (IBC) arrays have been developed by Raytheon Vision Systems for the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). These devices are also suitable for other low-background applications. The Si:As IBC detectors have a pixel dimension of 25 μm and respond to infrared radiation between 5 and 28 μm. Detector performance results are discussed, including response and dark current as a function of detector bias and relative spectral response. The features of the matching 1024 x 1024 Readout Integrated Circuit (ROIC) features are discussed. Noise data from the University of Rochester are shown with the ROIC operating at 7 K. Sensor Chip Assembly (SCA) data are presented showing noise, response uniformity, and dark current. Design details of a companion 1024 x 1024 array suitable for high-background, ground-based astronomy will also be revealed for the first time. This array will have a large well capacity and be capable of high frame rates.

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.

Mosaic packaging for large-format infrared devices

The desire for larger and larger format arrays for astronomical observatories - both ground and space based - has fueled the development of very large focal plane array (FPA) packaging technology. This has generated new designs and the use of new materials suitable for high reliability and long thermal cycle performance when exposed to operating temperatures from ambient to below 10 Kelvin. We present the design and performance of a series of package designs meeting these requirements evolving from single large mega-pixel arrays through the multiple detector arrays utilizing 4-side butting. This butting arrangement permits future detector arrays of significant size of approaching a meter on a side for infrared astronomy. This packaging technology and the use of thermally compatible materials enable the large format packaging of all detector and Readout Integrated Chip (ROIC) combinations in current production. Current and future applications include the Mid-Infrared Instrument (MIRI) detector for the James Webb Space Telescope (JWST) mission, the 16 VIRGO detector focal planes for the Visible and Infrared Survey Telescope for Astronomy (VISTA) IR survey telescope and future applications such as the Supernova Acceleration Probe (SNAP) mission.

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.

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.