Quantum Well Infrared Photodetectors Research Articles

Enhanced response over wavelength range of 7–12 µm for quantum wells in asymmetric micro-pillars

Efficient coupling in broad wavelength range is desirable for wide-spectrum infrared light detection, yet this is a challenge for intersubband transition in semiconductor quantum wells (QWs). High-Q cavities mostly intensify the absorption at peak wavelengths but with shrinking bandwidth. Here, we propose a novel approach to expand the operating spectral range of the Quantum Well Infrared Photodetectors (QWIPs). By processing the QWs into asymmetric micro-pillar array structure, the device demonstrates a substantial enhancement in spectral response across the wavelength from 7.1 µm to 12.3 µm with guided mode resonance (GMR) effects. The blackbody responsivity is then increased by 3 times compared to that of the 45° polished edge-coupled counterpart. Meanwhile, the dark current density remains unchanged after the deep etching process, which will benefit the electrical performance of the detector with reduced volume duty ratio. In contrast to the symmetric micro-pillar array that contains simple resonance mode, the detectivity of QWIP in asymmetric pillar structure is found to be improved by 2-4 times within the range of 9.5 µm to 15 µm.

Long-wave infrared laser irradiation damage effect on GaAs/AlGaAs quantum well infrared photodetector

The damage effect and mechanism of laser irradiation on long-wave focal plane array (FPA) GaAs/AlGaAs quantum well infrared photodetector (QWIP) were preliminarily explored by using numerical simulation and experiment methods. Piecewise functions were employed to simulate the complex boundary structure of the QWIP, enabling the numerical simulation investigation of mono-pulse, nano-second, long-wave infrared laser irradiation damage effect on the QWIP. The highest QWIP temperature, the highest surface temperature and the maximum circumferential thermal stress were analyzed in relation to laser energy density. The pulse average energy density thresholds of thermal decomposition damage, melting damage and thermal stress-induced damage were theoretically obtained. Preliminary experiments were then conducted by using a mono-pulse, nano-second, 7.2 μm all-solid-state long-wave infrared laser. The experimental results revealed a point-shape damage in QWIP response measurement after the irradiation by a laser pulse of average energy density 1.30 J cm−2, due to the decomposition of GaAs. At a higher average energy density 5.42 J cm−2, both melting and stress-induced damages appeared, with the damage morphology predominantly influenced by stress-induced damage, resulting in the occurrence of blind pixels or the losing of pixels. Furthermore, at laser pulse average energy density 12.48 J cm−2, line-shape damage of the QWIP was observed.

Multi-Mode Long-Wavelength GaAs/AlGaAs Quantum Well Infrared Photodetectors for Circular Polarization Detection

We present an integrated device combining a double L-shaped chiral metasurface with long-wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs), achieving a circular polarized extinction ratio (CPER) as high as 45 in the long-wavelength infrared range of 7–9 μm. The unit of the chiral metasurface array consists of two structurally identical L-shaped gold structures with central symmetry. The CPER of the double L-shaped QWIPs is 14 times higher than that of a single L-shaped QWIP. The device operates in three modes within the detection band: the microcavity mode, the surface plasmon polariton (SPP) mode, and the hybrid mode. The double L-shaped chiral structure selects and reflects a small portion of left-handed circularly polarized light (LCP), while the majority enters the device and excites SPP modes with the bottom gold grating layer, leading to an absorption enhancement. In contrast, right-handed circularly polarized light (RCP) is mostly reflected with limited excitation of SPP waves. QWIPs exhibit a peak absorption of 0.8 and a coupling efficiency of 2700% in the active region of the quantum well due to the combined effects of the microcavity and SPP modes, in which the SPP mode plays a dominant role. The proposed device maintains high circular polarization discrimination capability under large incident angles and can be applied in spectral imaging.

Bias-Tunable Quantum Well Infrared Photodetector.

With the rapid advancement of Artificial Intelligence-driven object recognition, the development of cognitive tunable imaging sensors has become a critically important field. In this paper, we demonstrate an infrared (IR) sensor with spectral tunability controlled by the applied bias between the long-wave and mid-wave IR spectral regions. The sensor is a Quantum Well Infrared Photodetector (QWIP) containing asymmetrically doped double QWs where the external electric field alters the electron population in the wells and hence spectral responsivity. The design rules are obtained by calculating the electronic transition energies for symmetric and antisymmetric double-QW states using a Schrödinger-Poisson solver. The sensor is grown and characterized aiming detection in mid-wave (~5 µm) to long-wave IR (~8 µm) spectral ranges. The structure is grown using molecular beam epitaxy (MBE) and contains 25 periods of coupled double GaAs QWs and Al0.38Ga0.62As barriers. One of the QWs in the pair is modulation-doped to provide asymmetry in potential. The QWIPs are tested with blackbody radiation and FTIR down to 77 K. As a result, the ratio of the responsivities of the two bands at about 5.5 and 8 µm is controlled over an order of magnitude demonstrating tunability between MWIR and LWIR spectral regions. Separate experiments using parameterized image transformations of wideband LWIR imagery are performed to lay the framework for utilizing tunable QWIP sensors in object recognition applications.

Multiplied absorption in subwavelength self-grating-coupled multi-layer quantum wells with reduced dark current

Light detection through intersubband transition faces combined demands of retaining normal incidence coupling, enhancing absorption, and suppressing dark current which is usually fulfilled by separate parts in devices. In this paper, 50-period GaAs/AlGaAs quantum well (QW) layers are designed and fabricated into arrays of subwavelength columns, which induces resonant mode to confine the infrared light inside the columns with strengthened electric field component in the z-direction. The self-grating-coupled QWs exhibit broadened absorption in the long wavelength range with peak absorption increased by 4.5 times at 8.7 μm relative to that of the 45⁰ polished edge-coupled counterpart. Meanwhile, the dark current is reduced by 51% due to the reduction of the electrical area. With the joint benefits of guiding and compressing incident light in squeezed volumes, it’s demonstrated that the dark current limited specific detectivity (Ddark∗) of quantum well infrared photodetectors (QWIPs) could be raised by 6.4 times when merged into photonic structures.

Growth of κ-([Al,In]xGa1-x)2O3 Quantum Wells and Their Potential for Quantum-Well Infrared Photodetectors.

The wide band gap semiconductor κ-Ga2O3 and its aluminum and indium alloys have been proposed as promising materials for many applications. One of them is the use of inter-sub-band transitions in quantum-well (QW) systems for infrared detectors. Our simulations show that the detection wavelength range of nowadays state of the art GaAs/AlxGa1-xAs quantum-well infrared photodetectors (QWIPs) could be substantially excelled with about 1-100 μm using κ-([Al,In]xGa1-x)2O3, while at the same time being transparent to visible light and therefore insensitive to photon noise due to its wide band gap, demonstrating the application potential of this material system. Our simulations further show that the QWIPs efficiency critically depends on the QW thickness, making a precise control over the thickness during growth and a reliable thickness determination essential. We demonstrate that pulsed laser deposition yields the needed accuracy, by analyzing a series of (InxGa1-x)2O3 QWs with (AlyGa1-y)2O3 barriers with high-resolution X-ray diffraction, X-ray photoelectron spectroscopy (XPS) depth profiling, and transmission electron microscopy (TEM). While the superlattice fringes of high-resolution X-ray diffraction only yield an average combined thickness of the QWs and the barrier and X-ray spectroscopy depth profiling requires elaborated modeling of the XPS signal to accurately determine the thickness of such QWs, TEM is the method of choice when it comes to the determination of QW thicknesses.

Auto-Calibrated Charge-Sensitive Infrared Phototransistor at 9.3 µm.

Charge-sensitive infrared photo-transistors (CSIP) are quantum detectors of mid-infrared radiation (λ=4 µm-14 µm) which have been reported to have outstanding figures of merit and sensitivities that allow single photon detection. The typical absorbing region of a CSIP consists of an AlxGa1-xAs quantum heterostructure, where a GaAs quantum well, where the absorption takes place, is followed by a triangular barrier with a graded x(Al) composition that connects the quantum well to a source-drain channel. Here, we report a CSIP designed to work for a 9.3 µm wavelength where the Al composition is kept constant and the triangular barrier is replaced by tunnel-coupled quantum wells. This design is thus conceptually closer to quantum cascade detectors (QCDs) which are an established technology for detection in the mid-infrared range. While previously reported structures use metal gratings in order to couple infrared radiation in the absorbing quantum well, here, we employ a 45° wedge facet coupling geometry that allows a simplified and reliable estimation of the incident photon flux Φ in the device. Remarkably, these detectors have an "auto-calibrated" nature, which enables the precise assessment of the photon flux Φ solely by measuring the electrical characteristics and from knowledge of the device geometry. We identify an operation regime where CSIP detectors can be directly compared to other unipolar quantum detectors such as quantum well infrared photodetectors (QWIPs) and QCDs and we estimate the corresponding detector figure of merit under cryogenic conditions. The maximum responsivity R = 720 A/W and a photoconductive gain G~2.7 × 104 were measured, and were an order of magnitude larger than those for QCDs and quantum well infrared photodetectors (QWIPs). We also comment on the benefit of nano-antenna concepts to increase the efficiency of CSIP in the photon-counting regime.

Mid-Infrared Frequency Combs based on Single Section Interband Cascade Lasers

In this work we show Frequency Comb (FC) and short pulsed operation of mid-infrared Interband Cascade Lasers (ICLs) in a single long section. This is through the use of an adapted ultrafast Quantum Well Infrared Photodetectors (QWIPs), and correlating the microwave beatnotes with high resolution spectra of the ICL. In particular, we will show active mode-locking (ML) of single -section ICL that does not require RF optimisation of the ICL device and highlight its temporal characteristics using Shifted Wave Infrared Fourier Transform Spectroscopy (SWIFTS) analysis to reconstruct the intensity in the time domain.

High-Discrimination Circular Polarization Detection Based on Dielectric-Metal-Hybrid Chiral Metamirror Integrated Quantum Well Infrared Photodetectors.

Circular polarization detection enables a wide range of applications. With the miniaturization of optoelectronic systems, integrated circular polarization detectors with native sensitivity to the spin state of light have become highly sought after. The key issues with this type of device are its low circular polarization extinction ratios (CPERs) and reduced responsivities. Metallic two-dimensional chiral metamaterials have been integrated with detection materials for filterless circular polarization detection. However, the CPERs of such devices are typically below five, and the light absorption in the detection materials is hardly enhanced and is even sometimes reduced. Here, we propose to sandwich multiple quantum wells between a dielectric two-dimensional chiral metamaterial and a metal grating to obtain both a high CPER and a photoresponse enhancement. The dielectric-metal-hybrid chiral metamirror integrated quantum well infrared photodetector (QWIP) exhibits a CPER as high as 100 in the long wave infrared range, exceeding all reported CPERs for integrated circular polarization detectors. The absorption efficiency of this device reaches 54%, which is 17 times higher than that of a standard 45° edge facet coupled device. The circular polarization discrimination is attributed to the interference between the principle-polarization radiation and the cross-polarization radiation of the chiral structure during multiple reflections and the structure-material double polarization selection. The enhanced absorption efficiency is due to the excitation of a surface plasmon polariton wave. The dielectric-metal-hybrid chiral mirror structure is compatible with QWIP focal plane arrays.

High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices

Free-space optical communication is a very promising alternative to fiber communication systems, in terms of ease of deployment and costs. Midinfrared light has several features of utter relevance for free-space applications: low absorption when propagating in the atmosphere even under adverse conditions, robustness of the wavefront during long-distance propagation, and absence of regulations and restrictions for this range of wavelengths. A proof-of-concept of high-speed transmission taking advantage of intersubband devices has recently been demonstrated, but this effort was limited by the short-distance optical path (up to 1 m). In this work, we study the possibility of building a long-range link using unipolar quantum optoelectronics. Two different detectors are used: an uncooled quantum cascade detector and a nitrogen-cooled quantum well-infrared photodetector. We evaluate the maximum data rate of our link in a back-to-back configuration before adding a Herriott cell to increase the length of the light path up to 31 m. By using pulse shaping, pre- and post-processing, we reach a record bitrate of 30 Gbit s − 1 for both two-level (OOK) and four-level (PAM-4) modulation schemes for a 31-m propagation link and a bit error rate compatible with error-correction codes.

The spontaneous polarization of In-doped κ-Ga2O3 by first-principles calculation

The crystal structure, band structure, density of states, and optical properties of κ-(Ga1−xInx)2O3 (x = 0, 0.125, 0.25, 0.5) were studied using the first-principles calculation based on the density functional theory. With the increase of In content x, the bandgap of κ-(Ga1−xInx)2O3 decreases, while the light absorption coefficient increases. The spontaneous polarization of κ-(Ga1−xInx)2O3 was calculated qualitatively using the Born effective charge. The results suggested that κ-(Ga1−xInx)2O3 is also a material with spontaneous polarization properties. The spontaneous polarization in the extended c-axis has increased 1.27 times, from 27.31 to 34.58 μC/cm2, with the increase of In content from 0 to 0.5. This work paves the way for modulating spontaneous polarization of wide bandgap semiconductors. It provides a theoretical basis for the potential application of κ-(Ga1−xInx)2O3 in high electron mobility transistors, quantum well-infrared photodetectors, and photovoltaic materials.

Electromagnetically induced transparency based quantum well infrared photodetectors

The characteristics of quantum well infrared photodetectors (QWIPs) which utilizing electromagnetically induced transparency (EIT) have been presented in this communication. Instead of direct absorption and creation of photoelectrons by the long wavelength infrared signal, the absorption properties of a short wavelength probe is modified by the infrared signal which subsequently creates photoelectrons. Owing to the indirect creation of photocurrent, the component of dark current which is due to thermionic emission is eliminated, thereby decreasing total dark current appreciably. The value of photocurrent depends on infrared signal power, bias voltage, probe detuning, and Rabi frequency of the control field. Results of this investigation may find potential applications in the development of terahertz infrared quantum well photodetectors under room temperature operation.

High circular polarization recognition quantum well infrared photodetector based on a chiral metamaterial microcavity

Circular polarization detection has important applications in the field of infrared detection. In this paper, a chiral metamaterial microcavity is designed to enhance the recognition of circularly polarized light (CPL) by a quantum well infrared photodetector (QWIP). By sandwiching the quantum well material and GaAs electrodes between a metallic chiral metamaterial and a gold substrate to form a microcavity structure, CPL discrimination can be achieved, and inter-subband absorption in the quantum well active region can also be improved. The electric field distribution is calculated and analyzed with the finite-difference time-domain method. Under the incidence of left circularly polarized light, the metallic chiral metamaterial on the surface excites the surface plasmon polariton (SPP) effect, which enhances the electric field ( E Z ) perpendicular to the growth direction of the quantum well, and the coupling efficiency can reach 950% at 14.9 µm wavelength. The SPP resonance wavelength matches the inherent response wavelength of the quantum well, so the inter-subband absorption of the quantum well is increased to about 0.9. At right circularly polarized light incidence, the coupling efficiency is only 105%, and the inter-subband absorption is only about 0.1 because the SPP effect is not effectively excited. Since chiral metamaterials can enhance the circular dichroism of quantum wells, when our designed structure is combined with QWIP, the circular polarization extinction ratio of QWIP can be increased to nine, which is much higher than 2.5 for a typical circular polarization detector. In addition, the inter-subband absorption will also be greatly improved under the incidence of CPL in a specific rotation direction. By optimizing the structural parameters, the resonance wavelength can be matched with the QWIP of different detection bands, which provides a new idea for the improvement of the performance of a quantum well infrared circular polarization photodetector in the long wave range.

Resonance-Enhanced Quantum Well Micropillar Array with Ultra-Narrow Bandwidth and Ultra-High Peak Quantum Efficiency

Infrared cameras with narrow-band detection capability are widely used for SF6 gas detection, which is an essential part of power equipment inspection. Narrow-band detection is usually achieved by a combination of quantum well infrared photodetectors (QWIPs) and narrow-band filters. Improving the quantum efficiency of QWIPs and reducing the detection bandwidth are important ways to improve camera performance. In this study, a back-incident-type device of quantum well micropillar array targeting at a 10.5 μm central wavelength is designed and studied by three-dimensional simulation. The operating mechanism of the device was determined by investigating the effect of the device geometry on the quantum efficiency. The enhanced absorption capability of the device mainly comes from the Fabry–Pérot resonance and the antireflection effect. The final device exhibits a remarkable peak quantum efficiency of 83% at 10.5 μm and an ultra-narrow spectral bandwidth of 0.2 μm. These excellent properties are achieved without an antireflective film and narrow-band filter, which can significantly improve the narrow-band capability and integration of the system; the dark current reduces to be 0.2762 times due to the low-duty cycle. These properties indicate that the structure of the quantum well micropillar array is of great significance to the development of QWIPs used in gas detection.

Small signal analysis of an infrared imaging device based on equivalent circuit model

This paper presents an analytical model of an infrared thermal imaging device. This device is composed of a Quantum Well Infrared Photodetector (QWIP), a Heterojunction Bipolar transistor (HBT) and a Light Emitting Diode (LED). It is called as QWIP-HBT-LED Optoelectronic Integrated Device. The device is modeled based on its equivalent circuit by considering a nonlinear gain HBT, early effect. Analytical expressions describing the current time response, rise time, and output derivative as a measure of device speed have been derived. The numerical results show that the transient performance of this device version is enhanced by the injected current from QWIP to the base of HBT, also the output current is increased with the increase of the gain and early coefficient of HBT, on the other hand, it degrades when the base recombination factor of HBT or the load resistance is increased. Also, the rise time increases when the current gain or the early coefficient is increased. This type of models can be exploited as a pixel in thermal image processing applications.

Breaking the interband detectivity limit with metasurface multi-quantum-well infrared photodetectors

Since their initial demonstration, metasurface quantum-well infrared photodetectors (QWIPs)—intersubband detectors integrated with plasmon cavities—using only a single quantum well (Nw = 1) have been considered the highest performance design. However, experimental confirmation via comparison of detectors with different Nw has not been performed. Here, we systematically compare Nw = 1 and Nw = 3 metasurface QWIPs with identical cavities and reveal the clear superiority of Nw = 3 detectors. While signal (responsivity) decreases with additional wells as predicted, the signal-to-noise-ratio (detectivity) increases due to drastically reduced noise. Thanks to the narrow spectral linewidth unique to metasurface QWIPs, our detectors can reach detectivity beyond the theoretical limits of interband detectors; our best detectors show maximum detectivities of 6.4×1010 cm Hz1/2/W at 7.0 μm, exceeding the interband limit of 5.3×1010 cm Hz1/2/W at the same wavelength.

A “Janus” double sided mid-IR photodetector based on a MIM architecture

We present a mid-IR (λ ∼ 8.3 μm) quantum well infrared photodetector (QWIP) fabricated on a mid-IR transparent substrate, allowing photodetection with illumination from either the front surface or through the substrate. The device is based on a 400 nm-thick GaAs/AlGaAs semiconductor QWIP heterostructure enclosed in a nanostructured metal–insulator–metal cavity and hosted on a mid-IR transparent ZnSe substrate. Metallic stripes are symmetrically patterned by e-beam lithography on both sides of the active region. The detector spectral coverage spans from λ ∼ 7.15 to λ ∼ 8.7 μm by changing the stripe width L—from L = 1.0 to L = 1.3 μm—thus frequency-tuning the optical cavity mode. Both micro-FTIR passive optical characterizations and photocurrent measurements of the two-port system are carried out. They reveal a similar spectral response for the two detector ports with an experimentally measured TBLIP of ∼200 K.

Stacked Dual-Band Quantum Well Infrared Photodetector Based on Double-Layer Gold Disk Enhanced Local Light Field.

We propose a stacked dual-band quantum well infrared photodetector (QWIP) integrated with a double-layer gold disk. Two 10-period quantum wells (QW) operating at different wavelengths are stacked together, and gold nano-disks are integrated on their respective surfaces. Numerical calculations by finite difference time domain (FDTD) showed that the best enhancement can be achieved at 13.2 and 11.0 µm. By integrating two metal disks, two plasmon microcavity structures can be formed with the substrate to excite localized surface plasmons (LSP) so that the vertically incident infrared light can be converted into electric field components perpendicular to the growth direction of the quantum well (EZ). The EZ electric field component can be enhanced up to 20 times compared to the incident light, and it is four times that of the traditional two-dimensional hole array (2DHA) grating. We calculated the enhancement factor and coupling efficiency of the device in the active region of the quantum well. The enhancement factor of the active region of the quantum well on the top layer remains above 25 at the wavelength of 13.2 μm, and the enhancement factor can reach a maximum of 45. Under this condition, the coupling efficiency of the device reaches 2800%. At the wavelength of 11.0 μm, the enhancement factor of the active region of the quantum well at the bottom is maintained above 6, and the maximum can reach about 16, and the coupling efficiency of the device reaches 800%. We also optimized the structural parameters and explored the influence of structural changes on the coupling efficiency. When the radius (r1, r2) of the two metal disks increases, the maximum coupling efficiency will be red-shifted as the wavelength increases. The double-layer gold disk structure we designed greatly enhances the infrared coupling of the two quantum well layers working at different wavelengths in the dual-band quantum well infrared photodetector. The structure we designed can be used in stacked dual-band quantum well infrared photodetectors, and the active regions of quantum wells working at two wavelengths can enhance the photoelectric coupling, and the enhancement effect is significant. Compared with the traditional optical coupling structure, the structure we proposed is simpler in process and has a more significant enhancement effect, which can meet the requirements of working in complex environments such as firefighting, night vision, and medical treatment.

Quantum well infrared detectors enhanced by faceted plasmonic cavities

Plasmonic cavities can prominently enhance the absorptance of quantum well infrared photodetectors (QWIPs). However, the total thickness of the semiconductor layers is usually in the deep subwavelength scale to ensure an intensified cavity mode, so the devices for the long wavelength infrared range usually contain a single quantum well. Although the relative enhancement is prominent, the absolute absorptance is not larger than common QWIPs and the ohmic loss is serious. Moreover, the ultra-thin semiconductor layer challenges the uniformity and the fabrication. Simply increasing the number of the QW stacks in a plasmonic cavity would probably ruin the critical coupling condition and result in an even worse situation. This work exhibits that creating real facets for the plasmonic cavities by etching away part of the semiconductors can enhance the light confinement capability and make the system with multiple quantum wells still close to a critical coupling status. Then, the quantum well absorptance is enhanced and the ohmic loss is suppressed. As experimentally demonstrated, the responsivity of a faceted plasmonic cavity integrated 4-stack QWIP at the wavelength around 15.5 μm is enhanced by 2.2 times with respect to an unfaceted one, and it is 12 times higher than that of a 45° edge facet coupled QWIP. In addition, the dark current is reduced by 32% due to the reduction of the photosensitive area. With the help of the enhanced light coupling, the specific detectivity D* initially increases with the number of QW stacks, reaches a peak around 3 stacks, and then drops back around 7 stacks to the similar level of the single stack structure.

Nature Allows High Sensitivity Thermal Imaging With Type-I Quantum Wells Without Optical Couplers: A Grating-Free Quantum Well Infrared Photodetector With High Conversion Efficiency

Quantum well infrared photodetectors (QWIPs) have facilitated thermal imagers with excellent pixel operability, uniformity and stability. The main disadvantage of the standard QWIP technology is the low conversion efficiency (CE) as a result of weak quantum efficiency (QE) and photoconductive gain inhibiting the utilization of the sensor for low background and/or high frame rate applications. The other problem is the requirement of an optical grating which loses its efficiency with decreasing pixel pitch, as well as limiting the performance of dual-band focal plane array (FPA) due to the wavelength dependence of the diffraction-grating coupling efficiency. The author reports a grating-free 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> pixel pitch <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$640\times 512$ </tex-math></inline-formula> mid-wavelength infrared (MWIR) QWIP FPA constructed with the InP/GaInP/In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.83</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.17</sub> As material system with normal incident radiation absorption ability. The pixels yielded peak QE, CE and specific detectivity of 23%, ~40% and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 10 ^{11}$ </tex-math></inline-formula> cmHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> /W (at ~80 K with f/2 optics) in spite of the absence of diffraction grating, substantially high cut-off wavelength (5.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> ) and broad spectral response ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \lambda /\lambda _{\mathbf {p}}=31$ </tex-math></inline-formula> %). Together with excellent (uncorrected) responsivity and noise equivalent temperature difference nonuniformities of 5.9% and 17%, the results illustrate tremendous improvement over the performance of the conventional MWIR QWIP FPA exhibiting great potential to revive the QWIP technology especially in dual-band imaging.