Soft x-ray quantum efficiency of silicon hybrid CMOS detectors

Abstract

Si Hybrid CMOS detectors (HCDs) are sensitive to X-rays between approximately 0.2 -20 keV. HCDs can provide superior performance to traditional CCDs in multiple areas: faster read out time, windowed read out mode, less susceptible to radiation & micrometeoroid damage, and lower power consumption. X-ray detectors designed for use in astronomical observatories must have an optical blocking filter to prevent the detectors from being saturated by optical light. We have previously reported on the successful deposition of an Al optical blocking layer directly onto the surface of HCDs. These blocking filters were deposited with multiple thicknesses from 180 -1000 Å and successfully block optical light at all thicknesses, with minimal impact expected on quantum efficiency at the energies of interest for these detectors. The thin Al layer is not expected to impact quantum efficiency at the energies of interest for these detectors. We report energy dependent soft X-ray quantum efficiency measurements for multiple HCDs with different optical blocking filter thicknesses.

Speedster-EXD: a new event-driven hybrid CMOS x-ray detector

“…This high depletion depth gives HCDs high quantum efficiency at energies above 6 keV, and they can be used to detect X-rays from 0.2 -20 keV. 7 The astronomy community has utilized HCD technology in the infrared and optical bands. 8,9 Infrared HCDs, which use a HgCdTe absorbing layer, have already flown on the Hubble Space Telescope 10 and the Wide-Field Infrared Survey Explorer (WISE) 11 mission, and they are also slated to fly on the James Webb Space Telescope (JWST).…”

Measuring the Quantum Efficiency of X-Ray Hybrid CMOS Detectors

“…The Mn Kα/Kβ and Al Kα measurements are both in good agreement with the previous QE measurements made on H1RG HCDs. 3,5 Many of these H1RGs have Al blocking filters, but have the same absorber layer thickness (100 µm); therefore, they should have similar QEs at moderate energies. All of these measurements represent high QE, comparable to other state-of-the-art X-ray detectors and meet the QE requirements for use in Lynx (≥ 85% 14 ).…”

“…Above 5 keV, almost all X-rays are transmitted through the inactive surface layer, and the QE is primarily determined by the fraction of X-rays absorbed by the Si absorbing layer. While the simple slab absorption model has proved accurate in past HCD QE measurements, 3,5,6 effects ignored by this simple 1D model (e.g., charge diffusion or pixel-to-pixel variations) may cause deviations from model values. In addition, uncertainties in surface layer thicknesses could cause the low-energy QE to deviate from the modeled values.…”

TheX-ray SurveyorMission: a concept study

“…The HDXI focal plane instrument for the X-ray Surveyor will provide a large field of view while simultaneously providing fine pixel resolution and high readout rate (instrument goals are listed in Table 2.) To satisfy these requirements, multiple active pixel sensor technologies are under consideration, including hybrid Complementary Metal Oxide Semiconductor or CMOS (PSU/Teledyne 38,39 ), monolithic CMOS 40 (SAO/Sarnoff), and 3-D tiered/layered bonded Si (MIT/Lincoln Labs 41,42,43 ) (Figure 5). HDXI requirements are similar to those of the Wide Field Imaging Spectrometer designed for the SMART-X concept, and a full description of competing technologies has been reviewed in the literature 44 .…”

“…Hybrid CMOS detectors, such those being developed by PSU/Teledyne, have shown high quantum efficiency (QE) across the entire soft X-ray bandpass, including reasonably high QE in the upper end of this energy range where response to Fe Kα becomes important 39 .…”