Optimized infrared photodetectors

Simulations lead to broader utility, lower power requirements, and greater quantum efficiency of the detector


Top view of corrugated QWIP pixels in an array

Quantum-well infrared photodetectors (QWIPs) have emerged as a mainstream technology for long-wavelength infrared detection. Utilizing the mature gallium arsenide material technology, QWIP focal plane array (FPA) cameras are amenable to low-cost and high-volume production. Today, QWIP cameras with resolution as high as 640×512 pixels are commonly available in the commercial market. Still, QWIP FPAs are far from optimized and improvements can be made for them to be useful in large-format arrays, to draw less power, to increase their quantum efficiency, and to make them more compatible with common readout electronics.

Army researchers, leaders in this field, have advanced the performance of QWIPs and optimized the material and pixel structures for QWIP FPAs to the point of producing a number of large-format 1024×1024 FPAs well-suited for high-speed imaging. The Army method uses computer simulation to determine the configuration of pixels in an array. Altering the configuration in the simulation allows for optimzation for a predetermined wavelength or wavelength range in the active region and thereby increases the quantum efficiency of the photodetector. The diffractive region is also simulated, with the program drawing on different material compositions and predetermined wavelengths in order to further increase efficiencies.

The numerous applications for QWIP arrays include detecting malignant tumors, monitoring crop health, monitoring food processing contamnation, identifying trace chemicals, measuring cloud layer emissivities (droplet/particle size, composition, height), tracking dust and sand particles, studying CO2 absorption, and many others.

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