High-performance nBn mid-wavelength infrared (MWIR) photodetectors and focal plane arrays (FPAs) based on an InAs/InAsSb type-II superlattice (T2SL) absorber and an AlSb/AlAsSb T2SL superlattice have been demonstrated. At 150 K, the photodetector exhibits 50% cutoff wavelength of 4.8 mu m, a peak responsivity of 1.72 A/W corresponding to a quantum efficiency of 56.9% at an applied bias of -0.1 V, and a dark current density of 1.38 & times; 10(-6) A/cm(2), which is 2 & times; Rule 07. The dark current-limited and f/2 blackbody (300 K background, 3-5 mu m band) specific detectivities reach 2.55 & times; 10(12) and 3.69 & times; 10(11) cm Hz(1/2)/W, respectively. A 15 mu m pitch, 640 & times; 512 format nBn FPA fabricated from the same wafer achieves a mean noise equivalent temperature difference of 13.9 mK and an operability of 99.8% at 150 K under f/2 optics. The nBn FPA enables imaging of room-temperature human targets up to 230 K with only two-point nonuniformity correction. This work demonstrates the significant potential of InAs/InAsSb superlattice-based nBn photodetectors and FPAs for thermoelectrically cooled MWIR imaging.

Abstract As communication rates continue to increase and wavelength-division multiplexing (WDM) becomes ubiquitous, the conventional fiber-optic O and C bands no longer suffice. The 2 $$\upmu$$ μ m wavelength region has emerged as a promising new window in silicon photonics to meet future high-capacity demands and support next-generation optical communication and sensing. Here, we present a high-speed, high-responsivity InGaAs/GaAsSb type-II superlattice (T2SL) photodetector heterogeneously integrated on silicon via micro-transfer printing ( $$\upmu$$ μ TP), achieving broadband operation from 0.8 to 2.5 $$\upmu$$ μ m. By introducing a cavity between backside Au reflector and low refractive index BCB, the broadband responsivity is significantly enhanced with a 57.9% increase at 2 $$\upmu$$ μ m overcoming the conventional trade-off between responsivity and bandwidth. The optimized device demonstrates responsivities of 0.85 A/W at 1.55 $$\upmu$$ μ m and 0.6 A/W at 2.0 $$\upmu$$ μ m, together with 3dB bandwidths of 17 GHz and 18.7 GHz, respectively, approaching the intrinsic carrier transit limit. A clear eye diagram at 50 Gbps further confirms the high-speed performance. These results establish a new benchmark in the responsivity–bandwidth trade-off for broadband photodetectors and demonstrate $$\upmu$$ μ TP as a versatile integration platform for future silicon photonic integrated circuits and optical systems.

High-sensitivity linear-mode avalanche photodiodes (APDs) that operate beyond 1.65 μm and up to 2 μm require a narrow bandgap that also gives rise to high dark currents, especially when subject to the large electric fields necessary for avalanche multiplication. This has led to increasing interest in separate absorption, charge, and multiplication (SACM) detectors where the narrow bandgap absorber has a low electric field and the wider bandgap multiplication region provides the gain. A systematic study of Al0.7In0.3As0.31Sb0.69 grown lattice-matched on GaSb as the multiplication layer has been undertaken on p-i-n structures varying in width from 0.1 to 1.5 μm and the ionization coefficients and excess noise extracted over a wide electric field range (195 kV/cm-830 kV/cm). When integrated with a lattice-matched Al0.3In0.7As0.64Sb0.36 absorption layer, such an SACM APD is found to demonstrate a quantum efficiency of 64% and 10% for the wavelengths of 1.55 and 2 μm, respectively, at punch-through, without any antireflection coating. The device shows a maximum avalanche gain of 197 with an excess noise of 3.1 at a gain of 10. Such APDs can be potentially used in a receiver for many photon-starved applications, including gas sensing and LiDAR.

Au gratings are widely employed as the primary architecture in infrared linear polarization detectors; however, they suffer from significant optical losses in the long-wave infrared range, resulting in limited extinction ratios. In this study, we present a highly polarization-sensitive Au/SiO2 double-layer linear grating integrated into InAs/GaSb superlattice-based long-wave infrared detectors. Finite-difference time-domain simulations demonstrate that by leveraging the Fabry-Perot resonance cavity within the SiO(2 )grating, the structure enhances the transmittance of TM-polarized light while suppressing that of TE-polarized light, thereby significantly improving the extinction ratio. Compared to conventional Au grating-based polarization detectors, the proposed device exhibits superior responsivity to TM-polarized light and a higher extinction ratio across the 8-14 mu m wavelength range. Specifically, the extinction ratio improves by a factor of 1.25 at 9.2 mu m. This approach offers an effective strategy for advancing high-performance long-wave infrared linear polarization detectors.

High-indium-content In0.83Ga0.17As is the key material for extended short-wave infrared (eSWIR) photodetectors operating in the 1.7–2.7 μm range. Here, we demonstrate a Ta2O5–SiO2 bilayer passivation structure, deposited by electron beam evaporation, on In0.83Ga0.17As PIN mesa photodetectors. The bilayer delivers stable dark current suppression across a wide bias range, maintaining a surface leakage current density of 2.2 × 10−6 A/cm2 at high bias and achieving a room-temperature sidewall resistivity up to 106 Ω cm. X-ray photoelectron spectroscopy reveals that lattice oxygen in Ta2O5 forms stable As–O bonds with surface arsenic atoms, effectively breaking Fermi-level pinning, while the outer SiO2 layer ensures long-term environmental stability. This work provides an efficient and scalable passivation route for high-In mesa-type eSWIR detectors. The device achieves a specific detectivity of 9 × 1011 Jones at 200 K.

InAs/GaInSb Type-II superlattice (T2SL) materials exhibit significant advantages in long-wave (LWIR) and very long-wave infrared (VLWIR) detectors. By optimizing molecular beam epitaxy (MBE) growth parameters and interface control techniques, a 50-period short-period superlattice (SL) structure composed of 10 monolayer (ML) InAs/ 7 ML Ga(0. 7)5In(0. 25)Sb was successfully grown at the GaSb reconstruction transition temperature. High-resolution X-ray dif- fraction (HRXRD) characterization revealed a lattice constant of 6. 108 & Aring; and a period thickness of 53. 53 & Aring; for the superlattice, with deviations from theoretical design values below 0. 2%. The lattice mismatch with the GaSb substrate was only 0. 197%. Atomic force microscopy (AFM) measurements demonstrated a root mean square (RMS) surface roughness of 1. 67 & Aring;, while photoluminescence (PL) spectroscopy indicated a bandgap of 89. 9 meV. Further more, a 12 ML InAs/5 ML Al0. 8In0.2Sb superlattice barrier material was epitaxially grown, exhibiting a lattice mismatch of 0. 067% with the GaSb substrate. Experimental results confirm that both 10 ML InAs/7 ML Ga(0. 7)5In(0. 25)Sb and 12 ML InAs/5 ML Al0. 8In0.2Sb superlattices exhibit excellent lattice compatibility with the GaSb substrate. The presence of mul- tiple satellite diffraction peaks and superior interface quality further validate the structural integrity of the materials. These findings provide a critical material foundation for the development of high-performance infrared detectors.

We fabricated a short-wave infrared (SWIR) focal plane array (FPA) based on an M-type superlattice and characterized its optoelectronic properties. Key considerations for applying three-dimensional (3D) noise analysis to SWIR devices are summarized, including response linearity fitting, two-point calibration, and noise source decomposition. Results show that temporal column noise dominates the noise budget, with detection capability limited by the readout circuit rather than dark current. This study provides a reproducible experimental procedure and data support for the engineering application of the 3D noise analysis method, enabling noise source localization and performance optimization of SWIR FPAs.

This study systematically investigates the influence of carbon content on the electrical and optical properties of Te-doped n-type GaSb single crystals grown by the liquid encapsulated Czochralski (LEC) method. Room-temperature Hall measurements reveal anomalous behavior in which high-purity samples exhibit lower mobility than their lower-purity counterparts. Supported by theoretical calculations based on the two-band model, we attribute this behavior to the reduced acceptor compensation in high-purity crystals. The relatively higher Fermi level in the low-compensation sample enhances the statistical occupation of the heavy-mass secondary L-valley, thereby degrading the overall mobility. Consequently, Hall data obtained at 77 K are found to more accurately reflect the intrinsic electrical properties. Optically, photoluminescence (PL) measurements indicate that carbon impurities occupy Sb sites (CSb), creating a competitive relationship that suppresses intrinsic defect complexes such as (VGaGaSb)2−. However, this suppression comes at the cost of enhanced non-radiative recombination and strong electrical compensation. These findings suggest that optimizing n-GaSb requires strictly minimizing carbon contamination while independently controlling intrinsic defects.

We report InAs/AlSb triple-barrier resonant tunneling diodes (TB-RTDs) exhibiting one-sided negative differential conductance (NDC) and pronounced zero-bias nonlinearity at room temperature. A peak current of 320.1 & micro;A is obtained at a negative collector bias of -0.34 V, with a peak-to-valley current ratio of 6.61. The observed polarity-selective transport is interpreted in terms of a resonance channel involving the first quasi-bound state (QBS) in the collector-side well and the second QBS in the emitter-side well. An absolute curvature coefficient of 23.14 V-1 is obtained at zero bias, indicating strong intrinsic rectification behavior. These results identify mixed-order quasi-bound-state coupling in asymmetric InAs/AlSb TB-RTDs as a viable route to polarity-selective NDC and strong zero-bias nonlinear response.

Abstract Broadband photodetection covering both visible and infrared wavelengths holds significant potential for sensing and reconnaissance applications that require simultaneous multiband imaging. However, extending the spectral response of a single infrared photodetector into the visible regime while maintaining low-noise operation at elevated temperatures remains a substantial challenge. This work presents an antireflection coating–Fabry–Pérot–guided-mode resonance (ARC-FP-GMR) hybrid-enhanced photodetector based on a back-illuminated InAs/GaSb type-II superlattice pπMn structure. This design synergistically combines the wavelength-selective enhancement of FP resonance with the lateral light confinement of GMR through a funnel-shaped microhole array grating fabricated on the epitaxial etch-stop and buffer layers, integrated with a bottom metal reflector to form an optical cavity. An additional SiO2 top layer further suppresses reflection in the visible band. The resulting GMR device achieves an average quantum efficiency of 66% across a 0.6–4.7 μm spectral range at 160 K, with a dark current density of 6.6 × 10–4 A/cm2 and a peak specific detectivity exceeding 2 × 1011 cm·Hz1/2/W. In addition, the device maintains a broadband detectivity above 1 × 109 cm·Hz1/2/W even at 250 K. Device-level simulations indicate a noise-equivalent temperature difference below 2 mK for a 1000 K target detection at 220 K. This study establishes a viable technical route toward high-performance broadband infrared detection systems for next-generation focal plane arrays.

We report a composite passivation scheme-O-2 plasma pretreatment followed by dielectric deposition-to suppress surface leakage in extended short-wave infrared (e-SWIR) InGaAsSb photodetectors. The compositely passivated devices exhibit significantly enhanced surface resistivities of 1805 Omega cm (O-2 plasma + SiO2) and 1793 Omega cm (O-2 plasma + Si3N4), 2.2 and 1.4 times higher than devices passivated with SiO2 alone (820 Omega cm) and Si3N4 alone (1293 Omega cm), respectively. Gated device analysis combined with dark current modeling indicates that the performance enhancement originates from the modulation of surface potential by the composite passivation, which suppresses the two dominant surface leakage currents: generation-recombination current in the surface space-charge region and tunneling current due to hole accumulation. At the temperature of 300 K, the devices exhibit a 100% cutoff wavelength of 3.2 mu m and a peak responsivity of 0.55 A/W at 2.2 mu m. The dark current density is 1.2 & times; 10(-2) A/cm(2) at a bias of -0.05 V. The best performance is achieved with combined O-2-plasma and Si3N4 passivation, yielding a peak specific detectivity of 7.7 & times; 10(9) Jones, which represents a 28.3% enhancement over the Si3N4-only device. These results confirm that the proposed composite passivation effectively suppresses surface leakage and enhances the performance of e-SWIR photodetectors. This approach shows promise for fabricating small-pixel infrared focal plane arrays capable of high-temperature operation.

The 2 μm spectral window has emerged as a promising candidate to mitigate the impending capacity crunch of the standard C-band. However, the development of high-speed photodetectors, specifically avalanche photodiodes (APDs), remains a bottleneck compared to the maturity of 2 μm fiber and amplifier technologies. In this paper, we report on a high-speed surface-illuminated APD operating at 2 μm, grown on an InP substrate with an InGaAs/GaAsSb type-II superlattice (T2SL) absorption layer. The device exhibits an extended cutoff wavelength exceeding 2.4 μm. The responsivity is measured to be 0.14 A/W at unity gain under illumination from a 2 μm laser. A 3-dB bandwidth of 10.2 GHz is achieved for a 20-μm diameter device. Furthermore, clear open eye diagrams are demonstrated at data rates up to 15 Gb/s.

Achieving a high signal-to-noise ratio is crucial for room-temperature mid-wave infrared (MWIR) InAs/GaSb type-II superlattice photodetectors. Although photon absorption can be improved by increasing the thickness of the absorber, the contradiction between the low absorption coefficient compared to the bulk material and the carrier diffusion length limits the further improvement of quantum efficiency. Here, we report a zinc sulfide (ZnS) anti-reflection (AR) coating-enhanced room-temperature MWIR p pi Mn photodetector based on InAs/GaSb type-II superlattice for carbon monoxide detection, where a ZnS AR layer integrated with buried electrodes is proposed that warrants a low-reflectivity surface with minimal additional processing cost, thereby improving the photon absorption without compromising the electrical properties. Near the cutoff wavelength, the optimized ZnS layer is further demonstrated to improve the utilization of low-energy photons. Consequently, integrating with the ZnS layer, the photodetector operating at room temperature exhibits a dark current density of 0.34 A/ cm2 and a quantum efficiency of 36 % at-50 mV bias, leading to a responsivity of 1.31 A/W and a specific detectivity of 2.8 x 109 cm Hz1/2/W at 4.6 mu m.

As an important III–V semiconductor material for infrared applications, gallium antimonide (GaSb) single crystals require high quality with excellent lattice perfection, making it necessary to establish an ideal thermal field during the liquid encapsulated Czochralski (LEC) growth process. In this study, global transient numerical simulations are carried out to analyze the effects of growth parameters on the temperature distribution, melt convection structure, and solid–liquid interface deflection during the LEC growth of 3‐inch‐diameter GaSb crystals. Additionally, an innovative bottom heater is introduced to optimize the thermal distribution. The simulation results demonstrate that the number of melt vortices decreases from three to two when the crucible rotation rate is 2 rpm, significantly reducing the solid–liquid interface deflection. A pulling rate of 8 mm/h reduces local overheating at the interface, thereby minimizing deflection and promoting stable growth. The addition of a bottom heater improves the melt temperature distribution, reduces melt flow intensity, and enhances interface flatness. The average etch pit density (EPD) of the 3‐inch (100) GaSb substrate is reduced from 2842 to 147 cm⁻ 2 after thermal field optimization, demonstrating a 94.8% reduction in dislocation density. This work establishes a scalable framework for the optimization of compound semiconductor crystal growth.

We demonstrate an advanced InGaAsSb extended short-wavelength infrared photodetector with novel complementary quantum barriers (CQB). The photodetector uses an InGaAsSb alloy as the absorber and GaSb/AlAsSb and InAs/AlSb superlattices as the complementary electron and hole barriers, respectively. The In0.28Ga0.72As0.25Sb0.75 absorber results in a 50

Avalanche photodiode (APD) is a kind of photodetector with important applications in optical communication, light detection and ranging (LIDAR) and other fields. APDs fabricated using the recently developed AlGaAsSb as the multiplication material exhibit excellent noise performance. In this work, we report a low-noise separate absorption, grading, charge, and multiplication (SAGCM) InGaAs/AlGaAsSb APD operating at 1550 nm. A double-mesa structure was fabricated to reduce the dark current. Numerical simulations were conducted to compare two different mesa-structured APDs. By analyzing the electric field distribution, it was found that the electric field at the edge of the multiplication region in the double-mesa APD is nearly 100 kV/cm lower than that of the single-mesa structure. Experimental results demonstrate that after device punch-through, the double-mesa APD's dark current can be reduced by up to four times compared to the single-mesa APD. Quantitative analysis of the dark current components in the AlGaAsSb APD further confirms that the low sidewall electric field in the double-mesa structure effectively suppresses the trap-assisted tunneling. Additionally, noise measurements indicate a k-value of approximately 0.014, which is significantly lower than that of traditional multiplication materials. This work provides preliminary validation for further performance improvements in low noise and low dark current AlGaAsSb APDs.

In this paper, a planar junction mid-wavelength infrared (MWIR) photodetector based on an InAs/GaSb type-II superlattices (T2SLs) is reported. The Intrinsic-pi MN superlattices was grown by the molecular beam epitaxy (MBE), followed with a ZnS layer grown by the chemical vapor deposition (CVD). The p-type contact layer was constructed by thermal diffusion in the undoped superlattices. The Zinc atom was successfully realised into the superlattice and a P pi MN T2SL structure was constructed. Furthermore, the effects of different diffusion temperatures on the dark current performance of the devices were researched. The 50% cut-off wavelength of the photodetector is 5.26 mu m at 77 K with 0 V bias. The minimum dark current density is 8.67 x 10-5 A/cm2 and the maximum quantum efficiency of 42.5%, and the maximum detectivity reaches 3.90 x 1010 cmHz1/2/W at 77 K. The 640 x 512 focal plane arrays (FPA) based on the planner junction were fabricated afterwards. The FPA achieves a noise equivalent temperature difference (NETD) of 539 mK.

Transmission electron microscopy was employed to investigate the micromorphological properties of subsurface lattice damage (SLD) in ground and rough polished indium arsenide (InAs) substrates. We show that the types and distributions of SLD defects in ground substrates and rough polished substrates are different, obviously, and are more complex compared to those in other hard-brittle materials. Remarkably, the depth of the SLD layer containing severely damaged regions, abnormal contrasts, and moiré fringes in rough polished substrates is three times deeper than that of the SLD layer composed of dislocations, stacking faults, and subsurface cracks in ground substrates. SLD in the rough polished substrate exhibits defect characteristics of lattice glide caused by the force applied during the polishing process. Formation mechanisms of SLD during grinding and rough chemical-mechanical polishing processes of the InAs substrates are discussed in view of removal behaviors of surface material and the evolution of stress fields.