Northrop Grumman Mission Systems
Track: Photonics Devices and Systems
Talk Title: Revival of Polycrystalline PbSe Technology for Low Cost MWIR FPA Production
Dr. Yoo holds a doctorate degree in electrical engineering from University of Illinois at Chicago, specializing in electro-optical materials and detectors. His PhD. thesis work included infrared detector design, modeling, simulation, fabrication and characterization in the spectral band range of far infrared to x/gamma-ray using II-VI based compound semiconductor materials. Since joining Northrop Grumman in 1997, Dr. Yoo has been active in threat warning detection and sensor development, EO/IR system integration, modeling, simulation, performance prediction and design optimization for military and remote sensing, such as for hyperspectral/multispectral sensing, polarimetry, interferometry, A/G and A/A targeting and tracking, IRST, threat warning, laser vibrometry, laser imaging and tracking, wave-front sensing and correction, and high resolution image reconstruction. Current responsibility includes for the development of low cost threat warning sensor using Pb-salt based materials for various platform protections.
Recently, Northrop Grumman Mission Systems demonstrated a thermo-electrically cooled (TEC) focal plane array (FPA) using polycrystalline PbSe directly deposited on read out integrated circuit (ROIC) wafers, and excellent performance of a 320×240 format FPA operating at 230 K was confirmed with a measured NEDT of 26 mK and a pixel operability of 98%(1). This is considered a world record for the sensitivity of MWIR detector operating at elevated temperatures. Furthermore, the demonstrated fabrication technology offers a low-cost production solution for MWIR detectors, compared to conventional molecular beam epitaxy (MBE), due to the unique detector structure and the features of polycrystalline detector materials. Highly sensitive polycrystalline PbSe material can be deposited directly on Si substrate or Si based ROIC wafers. A Chemical Bath Deposition (CBD) procedure developed by Northrop Grumman provides a method for high throughput and reproducibility, whereas the yield of other crystalline material production methods is determined by the level of defects generated during material growth. The polycrystalinity of PbSe detector material is very forgiving in material structural defects, while still achieving high IR responsivity at non-cryogenically cooled operating temperatures. Furthermore, thanks to the advances in ROIC technologies, we were able to demonstrate a new ROIC that can effectively filter out the dominant 1/f noise component as well as significantly reduce the pixel resistance nonuniformity commonly seen from polycrystalline detectors.