Infrared sensors utilizing Type II superlattice structures have gained increased attention in the past few years.
With the stronger covalent bonds of the III-V materials, greater material uniformity over larger areas is obtained as
compared to the weaker ionic bonding of the II-VI materials. Results obtained on GaSb/InAs Type II superlattices have
shown performance comparable to HgCdTe detectors, with the promise of higher performance due to reduced Auger
recombination and dark current through improvements in device design and material quality. In this paper, we discuss
advancements in Type II IR sensors that cover the 3 to >30 μm wavelength range. Specific topics covered will be device
design and modeling using the Empirical Tight Binding Method (ETBM), material growth and characterization, device
fabrication and testing, as well as focal plane array processing and imaging. We demonstrate high quality material with
PL linewidths of ~20 meV, x-ray FWHM of 20-40 arcsec, and AFM rms roughness of 1~.2 Å over a 20 μm×20μm area.
Negative luminescence at 10 μm range is demonstrated for the first time. Device external quantum efficiency of >30%,
responsivity of ~2A/W, and detectivity of 1011 Jones at 77K in the 10 μm range are routinely obtained. Imaging has been
demonstrated at room temperature for the first time with a 5 μm cutoff wavelength 256×256 focal plane array.
We report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi- insulating GaAs substrate for long wavelength IR detectors. Photoconductive detectors fabricated from the superlattices showed 80 percent cut-off at 11.6 micrometers and peak responsivity of 6.5 V/W with Johnson noise limited detectivity of 2.36 X 109 cmHz1/2/W at 10.7 micrometers at 78 K. The responsivity decreases at higher temperatures with a T-2 behavior rather than exponential decay, and at room temperature the responsivity is about 660 mV/W at 11 micrometers . Lower Auger recombination rate in this system provides comparable detectivity to the best HgCdTe detectors at 300K. Higher uniformity over large areas, simpler growth and the possibility of having read-out circuits in the same GaAs chip are the advantages of this system over HgCdTe detectors for near room temperature operation.
We report on the growth of InSb, InAsSb, and InTlSb alloys for infrared photodetector applications. The fabrication and characterization of photodetectors based on these materials are also reported. Both photoconductive and photovoltaic devices are investigated. The materials and detector structures were grown on (100) and (111)B semi-insulating GaAs and GaAs coated Si substrates by low pressure metalorganic chemical vapor deposition and solid source molecular beam epitaxy. Photoconductive detectors fabricated from InAsSb and InTlSb have been operated in the temperature range from 77 K to 300 K. The material parameters for photovoltaic device structures have been optimized through theoretical calculations based on fundamental mechanisms. InSb p-i-n photodiodes with 77 K peak responsivities approximately 103 V/W were grown on Si and (111) GaAs substrates. An InAsSb photovoltaic detector with a composition of x equals 0.85 showed photoresponse up to 13 micrometers at 300 K with a peak responsivity of 9.13 X 10-2 V/W at 8 micrometers . The RoA product of InAsSb detectors has been theoretically and experimentally analyzed.
In this paper, we report on the growth of InSb on (100) Si and (111)B GaAs substrates and the growth of InAsSb alloys for longer wavelength applications. The fabrication and characterization of photodetectors based on these materials are also reported. Both photoconductive and photovoltaic devices are investigated. The photodiodes are InSb p-i-n structures and InSb/InAs1-xSbx/InSb double heterostructures grown on (100) and (111)B semi-insulating GaAs and Si substrates by low pressure metalorganic chemical vapor deposition and solid source molecular beam epitaxy. The material parameters for device structures have been optimized through theoretical calculations based on fundamental mechanisms. InSb p-i-n photodiodes with peak responsivities approximately 103 V/W were grown on Si and (111) GaAs substrates. An InAsSb photovoltaic detector with a composition of x equals 0.85 showed photoresponse up to 13 micrometers at 300 K with a peak responsivity of 9.13 X 10-2 V/W at 8 micrometers . The RoA product of InAsSb detectors has been theoretically and experimentally analyzed.
High quality InSb has been grown by Molecular Beam Epitaxy and optimized using Reflection High Energy Electron Diffraction. A 4.8 micrometers InSb layer grown on GaAs at a growth temperature of 395 degree(s)C and a III/V incorporation ratio of 1:1.2 had an X-ray rocking curve FWHM of 158 arcsec and a Hall mobility of 92300 cm2V-1s-1 at 77 K, the best reported to date for InSb nucleated directly onto GaAs. InSb p-i-n structures of 5.8 micrometers grown under the same conditions demonstrated a X-ray Full Width at Half Maximum of 101 arcsec and 131 arcsec for GaAs and Si substrates, respectively, and exhibited excellent uniformity of +/- 3 arcsec over a 3' substrate. Prototype InSb p-i-n detectors on Si have been fabricated and have demonstrated photovoltaic response at 6.5 micrometers up to 200 K. These p-i-n detectors have also exhibited the highest D* for a device grown onto Si.
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