Interband Cascade Detectors Research Articles

Optical Characterization of the Interband Cascade LWIR Detectors with Type-II InAs/InAsSb Superlattice Absorber.

The long-wave infrared (LWIR) interband cascade detector with type-II superlattices (T2SLs) and a gallium-free ("Ga-free") InAs/InAsSb (x = 0.39) absorber was characterized by photoluminescence (PL) and spectral response (SR) methods. Heterostructures were grown by molecular beam epitaxy (MBE) on a GaAs substrate (001) orientation. The crystallographic quality was confirmed by high-resolution X-Ray diffraction (HRXRD). Two independent methods, combined with theoretical calculations, were able to determine the transitions between the superlattice minibands. Moreover, transitions from the trap states were determined. Studies of the PL intensity as a function of the excitation laser power allowed the identification of optical transitions. The determined effective energy gap (Eg) of the tested absorber layer was 116 meV at 300 K. The transition from the first light hole miniband to the first electron miniband was red-shifted by 76 meV. The detected defects' energy states were constant versus temperature. Their values were 85 meV and 112 meV, respectively. Moreover, two additional transitions from acceptor levels in cryogenic temperature were determined by being shifted from blue to Eg by 6 meV and 16 meV, respectively.

Demonstration of T2SLs InAs/InAsSb Based Interband Cascade Detector Supported by Immersion Lens for LWIR

This paper presents the performance of an interband cascade long-wavelength infrared detector designed for high operating temperatures supported by immersion lenses. The device is based on the “Ga-free” InAs/InAsSb type-II superlattice with highly doped p+/n+ superlattice tunneling junctions connecting adjacent stages. Detectivity of the multi-junction heterostructure detector exceeding 1010 cm Hz1/2/W was estimated at wavelength λ ~ 9 µm and T = 210 K and ~ 3 × 108 cm Hz1/2/W for T = 300 K, achieving a tenfold improvement in detectivity in comparison to a device without an immersion lens and 30-fold improvement in detectivity in comparison to the single-stage device.

The Interband Cascade Laser

We review the history, development, design principles, experimental operating characteristics, and specialized architectures of interband cascade lasers for the mid-wave infrared spectral region. We discuss the present understanding of the mechanisms limiting the ICL performance and provide a perspective on the potential for future improvements. Such device properties as the threshold current and power densities, continuous-wave output power, and wall-plug efficiency are compared with those of the quantum cascade laser. Newer device classes such as ICL frequency combs, interband cascade vertical-cavity surface-emitting lasers, interband cascade LEDs, interband cascade detectors, and integrated ICLs are reviewed for the first time.

An interband cascade platform permits on-chip mid-infrared dual-comb spectroscopy

Replacing the standard mercury-cadmium-telluride photodiode with an interband cascade detector brought a fully-integrated, broadband spectrometer one step closer to reality.

Long-Wavelength Interband Cascade Detector Architectures for Room Temperature Operation

We present a comparison of two interband cascade detectors optimized for long-wavelength infrared region: with equal and matched-absorbers. In matched-absorbers architecture, the first absorber determinates the thickness of the subsequent active layer, in order to meet equal quantum efficiency in all stages (QE condition). The simulations showed that quantum efficiency, for both types of architectures, decreases, while the detectivity versus number of stages increases. Detectors with equal absorbers (no QE condition) allow to build more stages in the cascade being the possible way to improve detectivity. On the other hand, structures with matched-absorbers show more flexibility in detectivity improvement by optimal selection of individual active layers. It is shown that structures assumed in this paper do not fully exploit the potential offered by the matched-absorbers approach. The optimal absorber selection allows to reach two times higher quantum efficiency. Moreover, interband cascade detectors optimized for long-wavelength were compared with intersubband quantum cascade infrared photodetectors and HgCdTe showing potential for room temperature operation.

Ultimate Performance of IB CID T2SLs InAs/GaSb and InAs/InAsSb Longwave Photodetectors for High Operating Temperature Condition

The highest performance of interband cascade detectors optimized for the longwave range of infrared radiation is investigated in this work to include decisive electric gain contribution. Presently, AIIIBV-type-II superlattice systems exhibit short carrier lifetimes limited by Shockley–Read–Hall generation–recombination processes. The maximum reported carrier lifetimes at 77 K for the InAs/GaSb and InAs/InAsSb type-II superlattices in longwave range correspond to ∼ 200 ns and ∼ 400 ns, respectively. We estimated theoretical detectivity of interband cascade detectors versus high operating temperatures, number of stages, absorber thickness, absorption coefficient and carrier lifetime; carrier lifetime were varied up to the reported value of MCT ∼ 1 μs. It has been shown that for room temperature the utmost performance–detectivity ∼ 1010 cmHz1/2/W for the optimized detector operating in the longwave range ∼ 10 μm and assuming electric gain effect could be reached.

Type-II superlattice detectors for free space optics applications and higher operating temperature conditions

The utmost limit performance of interband cascade detectors optimized for the longwave range of infrared radiation is investigated in this work. Currently, materials from the III–V group are characterized by short carrier lifetimes limited by Shockley-Read-Hall generation and recombination processes. The maximum carrier lifetime values reported at 77 K for the type-II superlattices InAs/GaSb and InAs/InAsSb in a longwave range correspond to ∼200 and ∼400 ns. We estimated theoretical detectivity of interband cascade detectors assuming above carrier lifetimes and a value of ∼1–50 μs reported for a well-known HgCdTe material. It has been shown that for room temperature the limit value of detctivity is of ∼3–4×1010 cmHz1/2/W for the optimized detector operating at the wavelength range ∼10 μm could be reached.

Ultra-thin infrared metamaterial detector for multicolor imaging applications.

The next generation of infrared imaging systems requires control of fundamental electromagnetic processes - absorption, polarization, spectral bandwidth - at the pixel level to acquire desirable information about the environment with low system latency. Metamaterial absorbers have sparked interest in the infrared imaging community for their ability to enhance absorption of incoming radiation with color, polarization and/or phase information. However, most metamaterial-based sensors fail to focus incoming radiation into the active region of a ultra-thin detecting element, thus achieving poor detection metrics. Here our multifunctional metamaterial absorber is directly integrated with a novel mid-wave infrared (MWIR) and long-wave infrared (LWIR) detector with an ultra-thin (~λ/15) InAs/GaSb Type-II superlattice (T2SL) interband cascade detector. The deep sub-wavelength metamaterial detector architecture proposed and demonstrated here, thus significantly improves the detection quantum efficiency (QE) and absorption of incoming radiation in a regime typically dominated by Fabry-Perot etalons. Our work evinces the ability of multifunctional metamaterials to realize efficient wavelength selective detection across the infrared spectrum for enhanced multispectral infrared imaging applications.

Mid-infrared metamorphic interband cascade photodetectors on GaAs substrates

Antimony-based mid-infrared interband cascade (IC) photodetectors fabricated on (001) GaAs substrates are reported. By using a “buffer-free” interfacial misfit array growth method, an overall good crystalline quality is obtained on the largely lattice-mismatched GaAs substrate. The GaAs-based IC detectors show comparable optical performance, with similar electrical performance at temperatures higher than 140 K, as compared to the reference devices grown on GaSb substrate. The GaAs-based IC detectors demonstrate dark current density of 2.63 × 10−6 A/cm2 at 180 K, which is about twice as compared to that grown on GaSb substrate, with Johnson-limited D* of 1.06 × 1011 Jones at 180 K and 4.0 μm. The results indicate that IC detector design is robust and relatively insensitive to the material quality, and metamorphic IC detector is viable for large-format infrared focal plane array applications.

Mid-Infrared Interband Cascade Photodetectors With Different Absorber Designs

We report an experimental investigation on the influence of absorber thicknesses in mid-infrared interband cascade (IC) photodetectors. The electrical and optical properties of these five-stage IC detectors are characterized in detail over a wide operating temperature range. The IC detectors are operational above 400 K under zero bias, with a 50% cutoff of 4.56 μm and external quantum efficiency (single pass, no antireflection coating) up to 10.1% at room temperature. The dark current in the IC detectors is at 10 μA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at -10 mV, with a Johnson-limited D* of 1.10 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Jones at 200 K. Our experimental results show that both the optical response and the noise performance in the quantum-engineered IC detectors improve with increased discrete absorber thicknesses. It is also suggested that the dark current in the IC detectors is determined by tunneling components at lower temperatures, and becomes diffusion-limited at higher temperatures.

Dark current in antimony-based mid-infrared interband cascade infrared photodetectors

The quantum-engineered interband cascade (IC) photodetector is a new type of infrared detectors with many unique and highly desirable features. The multi-stage design allows much flexibility in device optimization for different application environment, such as operation temperature, irradiance level, and possibly high-speed and fast frame-rate application scenarios. Many other distinctive features, such as excellent photo-carrier extraction and photovoltaic (zero-bias) operations, are also very attractive for high performance infrared imaging applications. In this paper, we report our experimental investigation on the dark current mechanisms in mid-wave infrared (MWIR) InAs/GaSb type-II superlattices based IC photodetectors. The electrical performance of MWIR IC detectors with several different designs are presented in detail. The dark current density in the MWIR IC detectors is as low as 4.26×10−8A/cm2 (1.44×10−3A/cm2) at −10mV, with Johnson-limited D∗ of 9.11×1011cmHz1/2/W (1.58×109cmHz1/2/W) at 140K (room temperature) and 3.6μm. Our results indicate that the dominating dark current in IC detectors is from tunneling components at lower temperatures, and changes to diffusion current at higher operating temperatures. Furthermore, our effort also shows that the dark current performance in IC devices can be improved substantially by refining the device design and implementations.

High operating temperature interband cascade focal plane arrays

In this paper, we report the initial demonstration of mid-infrared interband cascade (IC) photodetector focal plane arrays with multiple-stage/junction design. The merits of IC photodetectors include low noise and efficient photocarrier extraction, even for zero-bias operation. By adopting enhanced electron barrier design and a total absorber thickness of 0.7 μm, the 5-stage IC detectors show very low dark current (1.10 × 10−7 A/cm2 at −5 mV and 150 K). Even with un-optimized fabrication and standard commercial (mis-matched) read-out circuit technology, infrared images are obtained by the 320 × 256 IC focal plane array up to 180 K with f/2.3 optics. The minimum noise equivalent temperature difference of 28 mK is obtained at 120 K. These initial results indicate great potential of IC photodetectors, particularly for high operating temperature applications.

Band engineered HOT midwave infrared detectors based on type-II InAs/GaSb strained layer superlattices

We report on heterostructure bandgap engineered midwave infrared photodetectors based on type-II InAs/GaSb strained layer superlattices with high operating temperatures. Bandgap and bandoffset tunability of antimonide based systems have been used to realize photodiodes and photoconductors. A unipolar barrier photodiode, pBiBn, and an interband cascade photovoltaic detector have been demonstrated with a 100% cutoff wavelength of 5μm at 77K. The pBiBn detector demonstrated operation up to room temperature and the cascade detector up to 420K. A dark current density of 1.6×10−7A/cm2 and 3.6×10−7A/cm−2 was measured for the pBiBn and interband cascade detector, respectively, at 80K. A responsivity of 1.3A/W and 0.17A/W was observed at −30mV and −5mV of applied bias for pBiBn and cascade detector, respectively, at 77K. The experimental results have been explained by correlating them with the operation of the devices.

Midinfrared InAs∕GaSb type-II superlattice interband tunneling photodetectors

A photovoltaic InAs∕GaSb superlattice photodetector based on electron transfer using quantum energy levels and interband tunneling is presented: an interband tunneling detector. The quantum efficiency is about 7%, which is improved by ten times compared to the previous published interband cascade detectors. The R0A product is 0.03Ωcm2 at 200K and is comparable to that of state-of-the-art InAs∕GaSb superlattice photodiodes. Since the interband tunneling detector works without an applied bias, it is promising for small-pixel focal plane array applications.

Interband cascade detectors with room temperature photovoltaic operation

We investigated mid-infrared interband cascade laser structures as photodetectors, which are sensitive to normal incidence and operate in photovoltaic mode at room temperature. The proposed operation principle of these interband cascade detectors is based on the unique combination of interband photoexcitation and the much faster intersubband relaxation as well as interband tunneling recombination, which allows for the efficient collection of the photoexcited carriers. Peak responsivity and detectivity of 21 mA/W and 7.1×108cmHz1∕2∕W at λ=4.0μm are obtained for a device with cutoff wavelength of 4.4μm. Peak responsivity and detectivity of 46 mA/W and 1.4×109cmHz1∕2∕W at λ=3.0μm are obtained for another device with cutoff wavelength of 3.3μm. These detectors exhibit low noise (4.8×10−13A∕Hz1∕2) and a large product of the differential resistance and active area (19Ωcm2) at room temperature.