Johnson Noise Limited Detectivity Research Articles

A 10.7 μm InGaAs/InAlAs Quantum Cascade Detector

A 10.7μm quantum cascade detector based on lattice matched InGaAs/InAlAs/InP is demonstrated and characterized in terms of responsivity, resistivity and detectivity. The device operates in the 8–14 μm atmospheric window up to 140K and shows a peak reponsivity of 14.4mA/W at 78K. With a resistance-area product value of 159Ωcm2, the Johnson noise limited detectivity D*J is 2.8 × 109 Jones (cmHz1/2 W−1) at 78K.

High resistance AlGaAs/GaAs quantum cascade detectors grown by solid source molecular beam epitaxy operating above liquid nitrogen temperature

Quantum cascade detectors in the AlGaAs/GaAs material system have been grown by solid source molecular beam epitaxy. The growth direction of the active region is chosen carefully due to the existence of a doping concentration grade along the epilayers. For a 200 × 200 µm2 square mesa device, the detector operates above 90 K with a peak detection wavelength of 8.81 µm, and exhibits a high R0A about 4.5 × 106 Ω cm2 and a high Johnson noise limited detectivity D*J about 3.9 × 1010 Jones at this temperature.

Mid-infrared quantum cascade detectors for applications in spectroscopy and pyrometry

In this paper, we give an overview of quantum cascade detector technology for the near- and mid-infrared wavelength range. Thanks to their photovoltaic operating principle, the most advanced quantum cascade detectors offer great opportunities in terms of high detection speed, reliable room temperature operation, and excellent Johnson noise limited detectivity. Besides some important features dealing with their fabrication and their general characteristics, we will also briefly present some possibilities for performance improvement. Elementary theoretical considerations adopted from photoconductive detectors confirm that optimization of such devices always involves various trade-offs.

In As Sb ∕ Ga Sb heterostructure based mid-wavelength-infrared detector for high temperature operation

The properties of a midinfrared photodetector, based on a lattice matched n-N InAs0.91Sb0.09∕GaSb type-II heterostructure, were investigated. The relatively simple two layer structure shows very promising characteristics for sensitive and dual color infrared detection. I-V characteristics and spectral response were measured at the temperature range of 10–300K. High zero-bias resistance area product R0A of 2.5Ωcm2 was obtained at room temperature. The measured background limited infrared photodetection temperature was 180K corresponding to 4.1μm cutoff. Shot and Johnson noise limited detectivities corresponding to InAsSb absorption were measured to be 1.3×1010 and 4.9×109cmHz1∕2W−1 at 180 and 300K, respectively. An enhanced optical response with gain larger than unity was observed below 120K. Bias tunable dual color detection was demonstrated at all measured temperatures.

16.5 μ m quantum cascade detector using miniband transport

The authors report on an InP based photovoltaic quantum cascade detector operating at 16.5μm and using miniband-based vertical transport. This concept allowed the construction of a longitudinal optical phonon extraction stair with two rungs without touching on a high device resistance. At 10K, they observed a responsivity of 1.72mA∕W and a Johnson noise limited detectivity of 2.2×109 Jones. Altogether, this design resulted in detection at temperatures of up to 90K with a lower bandwidth limit of 200MHz imposed by the measurement setup.

Quantum cascade detectors

A photovoltaic intersubband detector based on electron transfer on a cascade of quantum levels is presented which we called a Quantum Cascade Detector (QCD). The highest photoresponse of intersubband transition based photovoltaic detectors is demonstrated: 44 mA/W at zero applied bias. Further improvements permit to suppress the leakage current and to increase the resistivity R 0 A. Useless cross-transitions have been eliminated finally leading to a high resistance narrow band photodetector with a Johnson noise limited detectivity at 50 K comparable to QWIPs. Because they work with no dark current, QCDs are very promising for small pixel and large focal plane array applications.

Type II InAs/GaSb superlattice photovoltaic detectors with cutoff wavelength approaching 32 μm

We report the most recent advance in the area of type II InAs/GaSb superlattice photovoltaic detectors that have cutoff wavelengths beyond 25 μm, with some at nearly 32 μm. The photodiodes with a heterosuperlattice junction showed Johnson noise limited peak detectivity of 1.05×1010 cm Hz1/2/W at 15 μm under zero bias, and peak responsivity of 3 A/W under −40 mV reverse bias at 34 K illuminated by ∼300 K background with a 2π field-of-view. The maximum operating temperature of these detectors ranges from 50 to 65 K. No detectable change in the blackbody response has been observed after 5–6 thermal cyclings, with temperature varying between 15 and 296 K in vacuum.

Room temperature operation of 8–12 μm InSbBi infrared photodetectors on GaAs substrates

We report the room temperature operation of 8–12 μm InSbBi long-wavelength infrared photodetectors. The InSbBi/InSb heterostructures were grown on semi-insulating GaAs (001) substrates by low pressure metalorganic chemical vapor deposition. The voltage responsivity at 10.6 μm was about 1.9 mV/W at room temperature and the corresponding Johnson noise limited detectivity was estimated to be about 1.2×106 cmHz1/2/W. The carrier lifetime derived from the voltage dependent responsivity measurements was about 0.7 ns.

Long-wavelength infrared photodetectors based on InSbBi grown on GaAs substrates

We demonstrate the operation of InSbBi infrared photoconductive detectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The fabricated photodetector showed a cutoff wavelength of 7.7 μm at 77 K. The responsivity of the InSbBi photodetector at 7 μm was about 3.2 V/W at 77 K. The corresponding Johnson-noise limited detectivity was 4.7×108 cm Hz1/2/W. The carrier lifetime was estimated to be about 86 ns from the voltage-dependent responsivity measurements.

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.

Room Temperature InAsxP 1-x-ySby/InAs Photodetectors with High Quantum Efficiency

Room temperature surface-illuminated InAsxP1-x-ySby/InAs photodiodes with an external quantum efficiency as high as 50–86% in a 1.83–3.53 µm wavelength range have been fabricated for the first time. Lattice matched heterostructures with a wide energy gap InAsPSb cap layer were grown on the InAs substrate using the liquid phase epitaxy technique. According to temperature dependence measurements for a 1 mm diameter photodiode, peak responsivities of 1.83–2.5 A/W have been realized in a temperature range of 296 to 200 K. The Johnson noise limited room temperature detectivities D* are deduced to be 1\\endash6 ×109 cm·Hz1/2/W at zero bias. It is demonstrated that the only loss of external quantum efficiency is from the reflection of the entrance face.

Long-wavelength InAsSb photoconductors operated at near room temperatures (200–300 K)

Long-wavelength InAs1−xSbx photoconductors operated without cryogenic cooling are reported. The devices are based on p-InAs1−xSbx/p-InSb heterostructures grown on (100) semi-insulating GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Photoreponse up to 14 μm has been obtained in a sample with x=0.77 at 300 K, which is in good agreement with the measured infrared absorption spectra. The corresponding effective lifetime of ≊0.14 ns at 300 K has been derived from stationary photoconductivity. The Johnson noise limited detectivity at λ=10.6 μm is estimated to be about 3.27×107 cm Hz1/2/W at 300 K.

InAs p-n diodes grown on GaAs and GaAs-coated Si by molecular beam epitaxy

InAs p-n diodes have been grown on GaAs and GaAs-coated Si substrates by molecular beam epitaxy. Transmission electron microscopy cross sections of the epilayers demonstrate a good structural quality. Photodiodes were obtained using a Be (p=5×1016 cm−3) and Si (n=3×1016 cm−3) doping scheme. The diodes exhibited 77 K zero-bias resistance area products of 2200 Ω cm2 for InAs/GaAs and 1500 Ω cm2 for InAs/GaAs/Si. The spectral response of the devices peaked at 2.95 μm with Johnson noise limited detectivities D* of 7.0×1011 cm Hz1/2/W for InAs/GaAs and 5.8×1011 cm Hz1/2/W for InAs/GaAs/Si. These results clearly demonstrate the feasibility of the monolithic integration of InAs infrared detectors and GaAs or Si read-out electronics.