1024 × 1024 Si:As IBC detector arrays for JWST MIRI

Abstract

1K × 1K Si:As Impurity Band Conduction (IBC) arrays have been developed by RVS for the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). MIRI provides imaging, coronagraphy, and low and medium resolution spectroscopy over the 5 -28 µm band. The IBC 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, covering an important Mid-IR region beyond the 1 -5 µm 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. We describe results of the development of a new 1024 × 1024 Si:As IBC array that responds with high quantum efficiency over the wavelength range 5 to 28 µm. The previous generation's largest, most sensitive infrared (IR) detectors at these wavelengths were the 256 × 256 / 30 µm pitch Si:As IBC devices built by Raytheon for the SIRTF/IRAC instrument 1 . Detector performance results will be discussed, including relative spectral response, Responsive Quantum Efficiency (RQE) vs. detector bias, and dark current versus temperature. In addition, Sensor Chip Assembly (SCA) data will be presented from the first Engineering SCAs. The detector ROIC utilizes a PMOS Source Follower per Detector (SFD) input circuit with a well capacity of about 2 × 10 5 electrons. The read noise of the "bare" MUX is less than 12 e-rms with Fowler-8 sampling at an operating temperature of 7 K. A companion paper by Craig McMurtry (University of Rochester) will discuss the details of SB305 MUX noise measurements 2 . Other features of the IBC array include 4 video outputs and a separate reference output with a frame rate of 0.36 Hz (2.75 sec frame time). Power dissipation is about 0.5 mW at a 0.36 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, SiC pedestal, and cable assembly with 51-pin MDM connector. 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.

The Brighter-Fatter Effect in the JWST MIRI Si:As IBC detectors I. Observations, impact on science, and modelling

“…1. Representation of MIRI detector architecture based on Petroff & Stapelbroek (1986); Love et al (2005); Rieke et al (2015); Gáspár et al (2021)]. The dimensions are not to scale.…”

“…Si:As IBC devices have extensive space flight heritage, having been used for example in all three instruments of the Spitzer space telescope, namely the Infrared Array Camera (IRAC), the Infrared Spectrograph (IRS), and the Multiband Imaging Photometer (MIPS). The high quantum efficiency of the Si:As IBC devices, in combination with the extensive wavelength range covered (5-28 µm) gives these devices a unique advantage (Love et al 2005;Gáspár et al 2021). Other detectors, such as the Teledyne Imaging Sensors' LWIR HgCdTe detector have a relatively higher quantum effi-…”

Characterization of the optical properties of the buried contact of the JWST MIRI Si:As infrared blocked impurity band detectors

“…We show a representation of the architecture of the MIRI detector arrays in Fig. 1, which is based on [2,3,11,12]. Photons pass through the anti-reflection coating on the detector back side, into the substrate, and then through the buried contact, into the infrared-active layer (detection layer).…”

“…The instrument employs three 1024x1024 pixel Si:As IBC detector arrays, which were manufactured by Raytheon Vision Systems (RVS). 2 Si:As IBC devices have extensive space flight heritage. Similar devices were used in all three instruments of the Spitzer space telescope, namely the Infrared Array Camera (IRAC), the Infrared Spectrograph (IRS), and the Multiband Imaging Photometer (MIPS).…”

“…The high quantum efficiency of the Si:As IBC devices, in combination with the extensive wavelength range covered (5-28 µm) gives these devices a unique advantage. 2,3 Other detectors, such as the Teledyne Imaging Sensors' LWIR HgCdTe detector have a relatively higher quantum efficiency, however, they cover a shorter wavelength range (the LWIR HgCdTe detector extends out to 13 µm). 4 It is important thus to understand the spectrophotometric response of the Si:As IBC device across the long wavelength range covered in order to maximize scientific output.…”