NASA awards RIT $1.1 million to develop IR detectors for space missions

Rochester, NY--The National Aeronautics and Space Administration (NASA) has awarded Rochester Institute of Technology (RIT) $1.1 million to advance a new family of large-format infrared (IR) detectors grown on silicon wafer substrates, a process developed by Raytheon Vision Systems (Goleta, CA). The resulting detectors could someday support future NASA missions to characterize dark matter and dark energy, and to hunt for Earthlike exoplanets.

RIT’s Center for Detectors will collaborate with Raytheon to design, fabricate, and test the hybrid detectors grown on silicon wafer substrates. Raytheon’s process for depositing light sensitive material on silicon wafers departs from standard detector technology that since the 1980s has relied upon small, expensive cadmium zinc telluride (CdZnTe) wafers.

"Right now, infrared detectors are so expensive that there are only a few on the world’s biggest telescopes -- Keck, Gemini, and the Very Large Telescope," says Donald Figer, director of the Center for Detectors at RIT. "Those are the only facilities that can afford them, and then they can only afford a few. They have big telescopes with big image planes and tiny detectors in the middle."

Up to 289 megapixels
The RIT-Raytheon device will have broad wavelength coverage that extends from the visible to the IR in arrays of 1024 x 1024 or 2048 x 2048 pixels -- the standard size in use today. The detectors will scale up to 14,000 by 14,000 pixels.

Last summer, RIT won a $1.2 million grant from the National Science Foundation for a similar collaboration between the Center for Detectors and Raytheon. The NSF award supports research advancing IR detector technology for use on ground-based telescopes and in the fields of remote sensing and medical imaging.

Now, support from NASA extends the research to space applications requiring radiation-hardened instruments. The technology could also enhance NASA’s Planetary Science and Earth Science space missions, the latter for characterization of weather, climate, and air pollution. The NASA-funded portion of the project will require the team to test and evaluate the detector in environments similar to conditions found in space. Figer and his engineers will also redesign the readout circuit to lower the device’s noise and signal interference.

For the last 15 years, scientists have pursued the use of silicon substitutes in the quest for large IR detectors. Until now, the crystal lattice mismatch between silicon and IR materials has stymied advancement, causing defects that generate higher dark current, and thus higher noise, reduced quantum efficiency, and increased image persistence. The lattice mismatch can cause photogenerated defects to masquerade as signals, which can get stuck, lost, or pop out of the lattice and present as false signals.

Raytheon’s technique for depositing light-sensitive material onto silicon substrates maintains high vacuum throughout the multistep process. The material growth is done using molecular-beam epitaxy (MBE).