Non-Destructive, Cryogenic 6-inch Wafer Level Screening and Measurement System of Infrared Detector materials

Sb-based III-V semiconductor Type-II superlattice (T2SL) materials with band structure-engineered device architectures are groundbreaking for infrared detectors and focal plane arrays (FPAs). T2SL FPAs have become very attractive candidates for various MDA/DOD sensor platforms including air, space, ships, and missiles. T2SL wafers, the starting materials of FPAs, are grown on large substrates using molecular beam epitaxy (MBE) in commercial growth foundries. A non-destructive, quick-turn, full-wafer screening capability will help them better serve MDA’s missions. The mapping measurement of minority carrier recombination lifetimes across an entire wafer is required to evaluate the semiconductor materials used for detector fabrication and to optimize the detector fabrication processing procedures. To fulfill these requirements, EPIR proposes to build a 6-inch, 300 K to 50 K temperature, minority carrier lifetime mapping system coupled with a cut-off wavelength measurement and mapping capability. The system will measure carrier recombination lifetimes down to 5 ns and their wafer-level distribution. We plan to use a pulse semiconductor laser with a rise/decay time of less than 1 ns as an excitation source and a long-wavelength-infrared (LWIR) laser as a probe light. The laser-generated excess carriers will lead to increased free carrier absorption related to the excess carrier concentration. Free carrier absorption decay can be detected using a fast (>200 MHz ) LWIR HgCdTe detector and collected using high-speed data acquisition electronics. In addition, broadband infrared light will be introduced at the same position on the sample and measure the transmission spectra in a 2-12 µm wavelength range using an EPIR-made LWIR linear detector array that will be mounted with infrared gratings in an optical multichannel analyzer configuration to quickly determine the cut-off wavelength. A cryogenic two-dimensional scanner will be built for mapping and scanning measurements over up to 6-inch or 150 mm diameter wafers in a single run. With further maturation of the system and technology, the proposed system can be integrated into other semiconductor material evaluation and device fabrication lines, including HgCdTe and other sensors that operate below room and/or at cryogenic temperatures to conduct temperature-dependent lifetime and absorption spectroscopy measurement in a non-destructive manner. Approved for Public Release | 23-MDA-11401 (14 Mar 23)