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.
Raytheon Vision Systems (RVS) has been developing high performance low background VisSWIR focal plane arrays suitable for the NASA WFIRST mission. These near infrared sensor chip assemblies (SCAs) are manufactured using HgCdTe on CdZnTe substrates with a 10 micron pixel pitch. WFIRST requirements are for a 4k x 4K format 4-side buttable package to populate a large scale 6 x 3 mosaic focal plane array of 18 SCAs. RVS devices will be compatible with the NASA developed FPA 4-side buttable package, and flight interface electronics. Initial development efforts at RVS have focused on a 2k x 2k format 10 micron pixel design based on an existing readout integrated circuit (ROIC) to demonstrate desired detector material performance at a relevant scale. This paper will provide performance results on the RVS efforts. RVS has successfully developed multiple 4k x 4k 10 micron pixel ROICs and we plan to demonstrate readiness to scale our design efforts to the desired 4k x 4k format for WFIRST in 2016.
Raytheon Vision Systems (RVS) has a long history of providing state of the art infrared sensor chip assemblies (SCAs) for the astronomical community. This paper will provide an update of RVS capabilities for the community not only for the infrared wavelengths but also in the visible wavelengths as well. Large format infrared detector arrays are now available that meet the demanding requirements of the low background scientific community across the wavelength spectrum. These detector arrays have formats from 1k x 1k to as large as 8k x 8k with pixel sizes ranging from 8 to 27 μm. Focal plane arrays have been demonstrated with a variety of detector materials: SiPiN, HgCdTe, InSb, and Si:As IBC. All of these detector materials have demonstrated low noise and dark current, high quantum efficiency, and excellent uniformity. All can meet the high performance requirements for low-background within the limits of their respective spectral and operating temperature ranges.
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.
Large format detector arrays are responsive uniformly over spectral 1-5μm wavelength
range and are available with RVS' high quality HgCdTe detector epitaxial layers on large
area 15 cm diameter wafers. Large wafers enable both low cost High Definition (HD)
staring FPAs, as well as the ability to approach giga-pixel format detector arrays with a
seamless 10cm ×10cm continuous image plane size possible. With a 15 cm diameter
detector substrate it is a straightforward growth path to a 5k×5k μm pitch 25 Mega-pixel
infrared focal plane array (FPA) with smaller pitches allowing even greater format along
the 10cm die length. This paper describes arrays 1.5 to 4 Mega-pixel infrared HgCdTe
developed by RVS for demanding higher performance applications. Performance data
for both the detector and ROIC for typical SWIR and MWIR FPAs operating at 85K will
be presented. This paper will provide FPA performance capability for small pitch large
format HgCdTe/Si detector arrays fabricated at RVS and manufacturing readiness low
cost Mega-pixel infrared FPAs for current and future wide FOV high-resolution systems.
We report on results of laboratory and field tests of dual- band MWIR/LWIR focal plane arrays (FPAs) produced under the Army Research Laboratory's Multidomain Smart Sensor Federated Laboratory program. The FPAs were made by DRS Infrared Technologies using the HgCdTe material system and by BAE Systems using QWIP technology. The HgCdTe array used the DRS HDVIPTM process to bond two single-color detector structures to a 640 X 480-pixel single-color read-out integrated circuit (ROIC) to produce a dual-band 320 X 240 pixel array. The MWIR and LWIR pixels are co-located and have a high fill factor. The images from each band may be read out either sequentially (alternating frames) or simultaneously. The alternating frame approach must be used to produce optimal imagery in both bands under normal background conditions. The QWIP FPA was produced using MBE-grown III-V materials. The LWIR section consisted of GaAs quantum wells and AlGaAs barriers and the MWIR section used InGaAs quantum wells with AlGaAs barriers. The detector arrays were processed with three ohmic contacts for each pixel allowing for independent bias control over both the MWIR and LWIR sections. The arrays were indium bump-bonded to an ROIC (specifically designed for two color operation) which puts out the imagery from both bands simultaneously. The ROIC has variable gain and windowing capabilities. Both FPAs were tested under similar ambient conditions with similar optical components. The FPAs were subjected to a standard series of laboratory performance tests. The relative advantages and disadvantages of the two material systems for producing medium-format dual-band FPAs are discussed.