Novel quantum-well infrared photodetector sensitive from 10 to 16 microns

Novel quantum-well infrared photodetector sensitive from 10 to 16 microns

Space-science and earth-observing missions of the future will need integrated long-wavelength quantum-well infrared photodetectors (QWIPs) in highly sensitive, low-power, large-area focal-plane arrays. Gallium arsenide (GaAs)/aluminum gallium arsenide has proven to be a useful material system for this application. Researchers at the Center for Space Microelectronics Technology at the Jet Propulsion Laboratory (Pasadena, CA) recently improved the structure of QWIPs to better handle dark current and improve detectivity, which results in higher operating temperatures.

Surnith Bandara and colleagues grew a broadband multiple-quantum-well structure by molecular-beam epitaxy. The device structure had 33 repeated layers of GaAs three-quantum-well units separated by AlGaAs barriers. The well thicknesses of the units were designed to respond at peak wavelengths near 13, 14, and 15 µm, respectively. The design permits wavelength broadening of 42% (a 400% improvement) and detectivity comparable to typical bound-to-quasibound QWI¥detectors with similar cutoff wavelengths. The researchers also were able to observe and explain two different gain mechanisms associated with photocurrent electrons and dark current electrons.