Antimony-based Interband Cascade (IC) photodetectors are emerging as viable candidates for highperformance infrared applications, especially at high operating temperatures. In our previous IC detector designs using InAs/GaSb Type-II superlattices, the quantum efficiency was relatively low as the designs were optimized for high signal to noise ratio. Here we report our recent development of low-noise mid-IR IC photodetectors with high external quantum efficiency. By adopting IC detectors with thicker absorber designs, the quantum efficiency of these mid-IR IC detectors has been increased up to 35%. These IC devices continue to have low-dark current and high temperature operations. Some further analysis on the device characteristics is also presented.
The InAs/GaSb type-II superlattice (T2-SL) based interband cascade (IC) photodetectors are emerging as a promising candidate for high performance infrared (IR) detectors, particularly for high operating temperature applications. In this paper, we present our latest progress on the development of high performance IC photodetectors in both mid- and longwave-IR. Our results show significant improvement in both the electrical and optical performance for the IC detectors. The mid-IR detectors show zero-bias operation, with external quantum efficiency as high as 11%. The dark current is 1.75 nA/cm2 at 120 K and -10mV, which shows over 5 times improvement over our previous best results. The Johnson-limited D* of the mid-IR detector is around 1.20×1011 Jones at 200 K, showing more than 10 times improvement over a wide temperature range. These mid-IR IC detectors have obtained background limited operation up to 210 K. Progress in longwave-IR IC detectors is also presented, which also demonstrates excellent electrical performance.
The Interband Cascade (IC) detector with InAs/Ga(In)Sb type-II superlattice (T2-SL) absorbers is a new type of high-performance infrared photodetector that has many unique features. In this IC detector design, the T2-SL absorber is sliced into multiple thinner segments that are sandwiched between electron and hole barriers, forming one stage. Multiple stages are electrically connected in series. The asymmetric energy-band alignment and ultra-fast carrier transport channel have enabled IC detectors to operate under/near zero-bias. The large lifetime contrast and the great design flexibility make IC detectors very suitable for high temperature operations. Our effort has led to the demonstration of mid-IR single pixel devices operating up to 450 K under zero-bias. These devices achieved superior electrical performance compared to HgCdTe technology at higher operation temperatures. In this presentation, we will discuss the new developments of low-noise mid-IR IC photodetectors and their focal plane arrays. Device studies on the influence of design on their optical and electrical performance will be discussed, and the most recent technical progress is also reported.
The objective of this study is to optimize the absorption in the active region of InAs/GaSb T2SL photodetectors for the
realization of high-performance MWIR devices. Two sets of MWIR (λ100% cut-off ~ 5.5μm at 77K) T2SL detectors were
realized; one set with varied detector absorber thickness, the other set with varied T2SL period. The T2SL material
quality was evaluated on the basis of room temperature photoluminescence (RTPL) and the high-resolution X-ray
diffraction (HRXRD) data. Then the device performance was compared using spectral response, dark current and
responsivity measurements. Finally, quantum efficiency was calculated and employed as a metric for the definition of
the optimal T2SL period and active region thickness. For the first part of the study, a homojunction pin architecture
based on 8 monolayers (MLs) InAs/8MLs GaSb T2SL was used. The thickness of the non-intentionally doped absorber
layers were 1.5μm, 2.5μm, and 3.5μm. For the second part of the study, unipolar barrier (pBiBn) devices were grown.
The thickness of the absorber region and the T2SL constituent InAs layer thicknesses were kept the same (1.5 μm and 8
MLs, respectively) whereas the T2SL constituent GaSb thickness was varied as 6 MLs, 8 MLs, and 10 MLs. We have
found that the pin detector with 2.5 μm thick absorber and the pBiBn detector with 8 ML InAs/ 8 ML GaSb T2SL
composition are, within the scope of this study, optimal for the realization of MWIR single-element devices and FPAs
with corresponding architectures.
For space-based imaging systems radiation tolerance to both displacement damage and total ionizing dose (TID) radiation effects continues to be a major performance concern. Here, the TID and proton irradiance tolerance of mid wave infrared interband cascade infrared photodetectors (ICIPs) based on InAs/GaSb type II strained-layer superlattice (T2SLS) absorbers is presented. Protons of energy of 63 MeV were used to irradiate the unbiased ICIP detectors at room temperature to a proton fluence of 7.5 x 1011 protons/cm2, corresponding to a TID of 100 kRads(Si). A comparison of the detector performance of a variety of ICIPs with different numbers of electron barrier sizes cascade stages is presented. Performance of detectors of varying size was characterized by dark current and quantum efficiency measurements at different temperatures. Results show changes, increase in dark current and a reduction in the quantum efficiency, consistent with an increase in the trap density.
Interband cascade infrared photodetectors (ICIPs) potentially offer mid-wave infrared detection at very high operating temperatures due to their nearly ideal photovoltaic operation. An ICIP typically makes use of several cascade stages grown in series, each of which consists of an active absorption region with a mid-wave cutoff wavelength, an intra-band relaxation region for electron transport and an inter-band tunneling region to enable electron transport to the next stage. The latter two also effectively act as a hole-barrier (hB) and an electron-barrier (eB), respectively, forming a preferential path for each carrier. Here, an ICIP with a relatively large eB was investigated. One of the key parameters to measure for detector performance is the noise spectrum, particularly to observe the behavior at low frequencies where the noise is often much larger than estimates based on the ideal shot noise expression would predict. This paper presents the results of noise spectrum measurements of differently sized ICIP devices, taken using an external trans-impedance amplifier with a cooled, internal impedance converter and a cooled feedback resistor. Measurements were taken at different operating temperatures and voltage biases in order to determine the noise-dependence on each.
InAs/GaSb type-II superlattices (T2-SLs) are of great interest as they provide a lot of band engineering flexibility. A wide variety of unipolar barrier structures have been investigated with this material system. In this report, we will present our recent work on the development of low noise long-wave infrared (LWIR) InAs/GaSb T2-SLs photodetectors. By adopting a so-called pBiBn design, the dark current of LWIR photodetectors is greatly suppressed. The LWIR pBiBn device has demonstrated a dark current density as low as 1.42×10-5 A/cm2 at -60 mV, and R0A of 5365 Ωcm2 at 76 K. A peak detectivity at 7.8 μm of 7.7×1011 cmHz1/2W-1 is obtained at 76 K. Further effort to reduce the operating bias is also reported. By refining the energy-band alignment, a 2-μm-thick LWIR pBiBn device has demonstrated a single pass (no AR coating) quantum efficiency of 20% at 10 μm under zero-bias at 77 K. We have recently extended our efforts to further reduce the dark current by using an interband cascade (IC) photodetector structure. Some further details about the device operation and results will be discussed.
There is an increasing interest in the development of high operating temperature (HOT) detectors with InAs/Ga(In)Sb Type-II superlattice (T2-SL) material systems. A wide variety of unipolar barrier structures have been investigated and successfully implemented in low-noise device architectures. In this paper, some of our recent work on the development of HOT mid-IR (MWIR) T2-SL photodetectors with interband cascade schemes will be summarized. In these structures, the discrete InAs/GaSb SL absorbers are sandwiched between quantum-engineered electron and hole barriers, which facilitate photovoltaic operation and efficient photo-carrier extraction. Even at its initial stage of development, such an advanced design has led to the demonstration of mid-IR photodetectors with background-limited operation above 150 K (300 K, 2π field-of-view), as well as above room temperature zero-bias operation. Further understanding of the device operation and design principles will also be discussed.
Over the last several years, owing to the implementation of advanced device architectures, antimony-based type-II
superlattice (T2-SL) infrared (IR) photodetectors and their focal plane arrays (FPAs) have achieved significant
advancements. Here we present our recent effort towards the development of high operating temperature (HOT)
mid-IR (MWIR) photodetectors, which utilizes an interband cascade scheme with discrete InAs/GaSb SL absorbers,
sandwiched between electron and hole barriers. This low-noise device architecture has enabled background-limited
operation above 150 K (300 K, 2π field-of-view), as well as above room temperature response in the mid-IR region.
The detector yields a dark current density of 1.10×10-7 A/cm2 (1.44×10-3 A/cm2) at -5 mV, and a Johnson-limited D*
of 2.22×1011 cmHz1/2/W (1.58×109 cmHz1/2/W) at 150 K (room temperature) and 3.6 μm, respectively. In this
presentation, we will discuss the operation principles of the interband cascade design and our most recent progress
in MWIR photodetectors toward high operating temperatures.
This paper describes our efforts on the development of low dark current long-wave infrared (LWIR) photodetectors based on type-II InAs/GaSb strained superlattices. By adopting a so-called pBiBn structure, a hybrid between the conventional PIN structure and unipolar barrier concepts, suppressed dark current and near-zero-bias operation are obtained, respectively. The LWIR photodetector has a dark current density as low as 1.42×10-5 A/cm2 at -60 mV, and R0A of 5365 Ωcm2 at 76 K. The measured peak detectivity at 10.2 µm of 8.7×1010 cmHz1/2W-1 is obtained at -60 mV at 76 K. To further improve the device performances, a newer design with longer cut-off wavelength targeted for near zero-bias was also realized. This 2-µm-thick device exhibits a quantum efficiency of 20% at 10 µm under zero-bias.
Interband cascade (IC) lasers take advantage of the broken band-gap alignment in type-II quantum wells to reuse injected electrons in cascade stages for photon generation with high quantum efficiency, while retaining interband transitions for photon emission without involving fast phonon scattering. As such, the threshold current density can be significantly lowered with high voltage efficiency, resulting in low power consumption. After about 18 years of exploration and development, IC lasers have now been proven to be capable of continuous wave operation at room temperature and above for a wide wavelength range of 2.9 to 5.7 μm in the mid-infrared spectral region. Here, we present our recent progress in InAs-based IC lasers, which use plasmon cladding layers to replace superlattice cladding layers, resulting in improved thermal dissipation and extended lasing wavelengths.
Interband cascade (IC) infrared (IR) photodetectors (ICIPs) are a new type of infrared detectors based on
quantum-engineered InAs/GaSb/AlSb heterostructures. They combine the features of conventional interband
photodiodes with the discrete nature of quantum-well IR photodetectors (QWIPs). The operation of ICIPs takes
advantage of fast intersubband relaxation and interband tunneling for carrier transport, and relatively slow interband
transitions (long lifetime) for photon generation. As such, ICIPs can be optimized for specific application
requirements, such as higher temperature operation or lower noise. By adopting a finite type-II InAs/GaSb
superlattice (SL) as the absorber, we have demonstrated mid-IR ICIPs with low noise and photovoltaic operation. In
this paper, we report some of our recent efforts in the development of mid-IR ICIPs for high temperature operations.
The ICIP devices with a cut-off wavelength of 3.8 μm exhibit a resistance-area product of 2.65×106 and 6.36×103Ωcm2 at 80 and 160 K, respectively.
Interband cascade (IC) lasers take advantage of the broken band-gap alignment in type-II quantum wells to
reuse injected electrons in cascade stages for photon generation with high-quantum efficiency, while retaining
interband transitions for photon emission without involving fast phonon scattering. Over the past several years,
significant progress has been made in developing efficient IC lasers, particularly in the 3-4 μm region where
continuous wave (cw) operation was achieved at above room temperature with low power consumption. In this
paper, we report our recent efforts in the development of IC lasers at longer wavelengths (4.3-7.5 μm) based on InAs
substrates and plasmon-waveguide structures. Cw operation of plasmon-waveguide IC lasers has been achieved at
temperatures up to 184 K near 6 μm. Also, improved thermal dissipation has been demonstrated with the use of the
plasmon waveguide structure.
Interband cascade (IC) infrared (IR) photodetectors (ICIPs) are a new type of detector that combines features of
conventional interband photodiodes with the discrete nature of quantum-well IR photodetectors (QWIPs) and IC
lasers. The operation of ICIPs takes advantage of fast intersubband relaxation and interband tunneling for carrier
transport, and relatively slow interband transitions (long lifetime) for photon generation. As such, ICIPs can be
tailored to optimize device performance for specific application requirements. We report our initial efforts in the
development of ICIPs. We have observed the photocurrent from an InAs-based IC laser with a cutoff wavelength
near 8 μm at 80 K, and significant photocurrent from GaSb-based ICIPs with cutoff wavelengths near 5 μm at 80 K
and 7 μm at above room temperature.
Interband cascade lasers are efficient and compact semiconductor mid-infrared (3-6 μm) light sources with low-power
consumptions. We report our recent progress in the development of interband cascade lasers with separate confinement
layers. Broad-area (0.1mmx1mm) lasers have been operated in cw mode at temperatures up to 213K near 3.36 μm. For
narrow ridge-waveguide (0.01mmx1.5mm) lasers, cw operation has been achieved at temperatures up to 266K near 3.43
μm, 260K near 3.7 μm, and 238K near 4.04 μm. The results on both broad-area and narrow-ridge IC lasers are
discussed in comparison with previous regular IC lasers without separate confinement layers.
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