Antimony-based materials for infrared photodetectors: Growth, characterization, fabrication, and analysis

Sb-based materials are investigated for infrared photodetectors capable of performance comparable or better than that of industry standard material systems such as mercury cadmium telluride (MCT) or Si microbolometers. The materials were grown by solid source molecular beam epitaxy on high quality, less expensive, large area substrate material such as GaAs and Si.; InSb was grown on 3&inches; GaAs substrates with material quality approaching that of bulk material as assessed using structural, electrical, and optical measurements. X-ray diffraction full widths at half maximum (FWHM) of ∼50 arcsec, electron mobilities of 125,000 cm2/V-s at 200K, and PL linewidths of ∼18 meV were obtained for InSb epilayers on GaAs.; In collaboration with an industrial partner, infrared imaging was obtained for the first time from heteroepitaxial InSb. A 256 x 256 array was bump bonded to a Si CMOS readout circuit resulting in infrared thermal imaging.; By incorporating As into the InSb lattice, the cutoff wavelength can be extended out to ∼12 μm at 300K. There is interest in infrared detectors that can operate in the long wavelength range without the need for cryogenic or thermoelectric cooling. Eliminating the cooling system improves reliability, decreases cost, and simplifies the overall system design. The main competitors to InAsSb are MCT and Si microbolometers. Although Si microbolometers achieve adequate detectivities at room temperature, the speed of the detector is not fast enough for applications such as projectile fuzes.; MCT is capable of high speed operation with detectivities in the 10 8 cm-Hz1/2/W range at 300K. However MCT suffers from material problems such as instability during growth and fabrication due to the ionic bonding of this II–VI material, as well as the very sharp dependence of cutoff wavelength on composition in the long wavelength infrared range. For these reasons, InAsSb has been investigated for uncooled infrared detector applications. Infrared detectors grown on GaAs substrates with InSb and AlInSb buffer layers have exhibited detectivities of 1–4 × 108 cm-Hz1/2/W at 300K. These detectivities are comparable to that obtained in state-of-the-art commercially available MCT detectors, which shows the great promise of the InAsSb material system for uncooled infrared detectors.