E. Michel

Growth and characterization of InGaAs/InGaP quantum dots for midinfrared photoconductive detector

We report InGaAs quantum dot intersubband infrared photodetectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The optimum growth conditions were studied to obtain uniform InGaAs quantum dots constructed in an InGaP matrix. Normal incidence photoconductivity was observed at a peak wavelength of 5.5 μm with a high responsivity of 130 mA/W and a detectivity of 4.74×107 cm H1/2/W at 77 K.

Growth and characterization of InAs/GaSb photoconductors for long wavelength infrared range

In this letter we report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi-insulating GaAs substrates for long wavelength infrared detectors. Photoconductive detectors fabricated from the superlattices showed photoresponse up to 12 μm and peak responsivity of 5.5 V/W with Johnson noise limited detectivity of 1.33×109 cm Hz1/2/W at 10.3 μm at 78 K.

High differential resistance type-II InAs∕GaSb superlattice photodiodes for the long-wavelength infrared

Type-II InAs∕GaSb superlattice photodiodes with a 50% cutoff wavelength ranging from 11to13μm are presented. Optimization of diffusion limited photodiodes provided superlattice structures for improved injection efficiency in direct injection hybrid focal plane array applications. Photodiodes with a cutoff wavelength of 12.9μm exhibit an R0A of ∼7Ωcm2 and a Johnson-limited detectivity of 4.03×1010cmHz1∕2W−1 operating at 77K. Quantum efficiency measurements indicate minority carrier diffusion lengths exceeding 3μm.

Molecular beam epitaxial growth of high quality InSb

In this letter we report on the growth of high quality InSb by molecular beam epitaxy that has been optimized using reflection high energy electron diffraction. A 4.8 μm InSb layer grown on GaAs at a growth temperature of 395 °C and a III/V incorporation ratio of 1:1.2 had an x‐ray rocking curve of 158 arcsec and a Hall mobility of 92 300 cm2 V−1 at 77 K. This is the best material quality obtained for InSb nucleated directly onto GaAs reported to date.

InSb infrared photodetectors on Si substrates grown by molecular beam epitaxy

The InSb infrared photodetectors grown heteroepitaxially on Si substrates by molecular beam epitaxy (MBE) are reported. Excellent InSb material quality is obtained on 3-in Si substrates (with a GaAs predeposition) as confirmed by structural, optical, and electrical analysis. InSb infrared photodetectors on Si substrates that can operate from 77 K to room temperature have been demonstrated. The peak voltage-responsitivity at 4 /spl mu/m is about 1.0/spl times/10/sup 3/ V/W and the corresponding Johnson-noise-limited detectivity is calculated to be 2.8/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W. This is the first important stage in developing InSb detector arrays or monolithic focal plane arrays (FPAs) on silicon. The development of this technology could provide a challenge to traditional hybrid FPAs in the future.

The molecular beam epitaxial growth of InSb on (111)B GaAs

The molecular beam epitaxial growth of InSb on (111)B GaAs has been investigated. It was found that for a given Sb/In ratio, a higher growth temperature was required for the growth of InSb on (111)B GaAs compared to that on (001) GaAs. This difference has been attributed to the bonding characteristics of the (111)B and (001) surface. Once growth had been optimized, it was found that the material characteristics of (111)B InSb were almost identical to that of (001) InSb, i.e., independent of orientation. For example, the x‐ray full width at half‐maximum and 300 K mobility had the same absolute values for (111) InSb and (001)InSb and followed the same dependence with the sample thickness. Te was found to be a well‐behaved n‐type dopant for (111)B InSb.

Type-II superlattice photodetectors for MWIR to VLWIR focal plane arrays

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.

Room‐temperature operation of InTlSb infrared photodetectors on GaAs

Long‐wavelength InTlSb photodetectors operating at room temperature are reported. The photo‐ detectors were grown on (100) semi‐insulating GaAs substrates by low‐pressure metalorganic chemical vapor deposition. Photoresponse of InTlSb photodetectors is observed up to 11 μm at room temperature. The maximum responsivity of an In0.96Tl0.04Sb photodetector is about 6.64 V/W at 77 K, corresponding to a detectivity of about 7.64×108 cm Hz1/2/W. The carrier lifetime in InTlSb photodetectors derived from the stationary photoconductivity is 10–50 ns at 77 K.

HIGH CARRIER LIFETIME INSB GROWN ON GAAS SUBSTRATES

We report on the growth of near bulklike InSb on GaAs substrates by molecular beam epitaxy despite the 14% lattice mismatch between the epilayer and the substrate. Structural, electrical, and optical properties were measured to assess material quality. X-ray full widths at half-maximum were as low as 55 arcsec for a 10 μm epilayer, peak mobilities as high as ∼125 000 cm2/V s, and carrier lifetimes up to 240 ns at 80 K.

Growth and characterization of InAs/GaSb type-II superlattice for long-wavelength infrared detectors

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.