AlInAsSb材料 缺陷能级 缺陷类型 受主型缺陷 受主缺陷能级 捕获界面参数 材料生长 APD

An avalanche photodetector (APD) based on the AlxIn1-xAsySb1-y digital alloy materials system has recently attracted extensive attention due to its extremely low excess noise. Device defects are a critical factor limiting the performance of APDs. In this work, we use low frequency noise spectroscopy (LFNS) to characterize the property of the defects in AlxIn1-xAsySb1-y APDs grown by molecular beam epitaxy (MBE) using the digital alloy technique. Based on low frequency noise spectroscopy results carried out before and after device oxidation, two surface defects and one bulk defect have been identified, which could provide useful information for the future optimization the material growth and device fabrication processes.

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We report the gain, noise, and dark current characteristics of random alloy Al0.79In0.21As0.74Sb0.26 (hereafter AlInAsSb)-based avalanche photodiodes (APDs) on InP substrates. We observe, at room temperature, a low excess noise corresponding to a k value (ratio of impact ionization coefficients) of 0.018 and a dark current density of 82 μA/cm2 with a gain of 15. These performance metrics represent an order of magnitude improvement of the k-value over commercially available APDs with InAlAs and InP multiplication layers grown on InP substrates. This material is also competitive with a recently reported low noise AlAsSb on InP [Yi et al., Nat. Photonics 13, 683 (2019)], with a comparable excess noise and a room temperature dark current density almost three orders of magnitude lower at the same gain. The low excess noise and dark current of AlInAsSb make it a candidate multiplication layer for integration into a separate absorption, charge, and multiplication layer avalanche photodiode for visible to short-wavelength infrared applications.

We report the noise characteristics of an AlInAsSb avalanche photodiode (APD) on an InP substrate. We observe low excess noise corresponding to an impact ionization coefficient ratio (k) of 0.012, and a dark current density of 55 μA/cm2 at a gain of 10 at room temperature. The performance of commercial APDs on InP substrates is limited by the excess noise and the performance of state of the art (SOA) APDs on InP substrates is limited by the dark current. The combination of low excess noise and low dark current of AlInAsSb leads to a significant performance improvement compared to commercial APDs and provides a potential candidate for low noise, SOA, commercial APDs for near-infrared applications. When combined in a separate absorber, charge and multiplication layer (SACM) architecture with an InGaAs absorption layer, the low noise characteristics of AlInAsSb point towards a superior InP substrate-based APD targeting 1.55 μm for applications such as optical communications and light detection and ranging (LiDAR).

Mid-wavelength infrared detection is useful for a variety of scientific and military applications. Avalanche photodiodes can provide an advantage for detection as their internal gain mechanism can increase the system signal-to-noise ratio of a receiver. We demonstrate a separate absorption, charge, and multiplication avalanche photodiode using a digitally-grown narrow-bandgap Al0.05InAsSb absorber for MWIR detection and a wide bandgap Al0.7InAsSb multiplier for low-excess-noise amplification. Under 2-μm illumination at 100 K the device can reach gains over 850. The excess noise factor of the device scales with a low k-factor of ~0.04. The unity-gain external quantum efficiency of the device peaks at 54% (1.02 A/W) at 2.35 μm and maintains an efficiency of 24% (0.58 A/W) at 3 μm before cutting off at ~3.5 μm. At a gain of 850 the device has a gain-normalized dark current density of 0.05 mA/cm2. This device achieves gains more than double state-of-the-art InAs detectors and gain-normalized dark current densities over two orders of magnitude lower than a previously reported MWIR Al0.15InAsSb-based detector.

By utilizing the low-noise benefits of staircase avalanche photodiodes (APDs) and the high-field tolerance of conventional APDs, a “cascaded multiplier” device has been grown and characterized showing significantly reduced excess noise compared to k ∼ 0 materials. Because it can withstand higher electric fields than a pure staircase APD, the gain values are not limited by the number of staircase steps in the device, and higher gains are demonstrated. In addition, the cascaded multiplier device shows reduced dark current to staircase devices of similar gain. Slight adjustments to the device design could increase the gain to even higher values—further improving the signal-to-noise ratio in the detector.

We report the design, epitaxial growth, and room-temperature operation of a high-gain AlInAsSb-based avalanche photodiode (APD) for short-wavelength infrared (SWIR) detection at 1.55 µm. The device employs SAGCM structure to confine the electric field within the multiplication region while suppressing dark current. High-quality AlInAsSb layers were grown on GaSb substrates by molecular beam epitaxy using a digital alloy approach, achieving excellent surface morphology (Ra < 0.2 nm) and uniform superlattice periodicity. Electrical characterization reveals a well-defined breakdown voltage near −17 V and a peak internal multiplication gain of 200 at 300 K under 0.2 mW illumination at 1550 nm—among the highest gains reported to date for antimonide-based APDs operating at room temperature. Variable-temperature dark current analysis indicates a transition from tunneling-dominated to thermally generated dark current as temperature increases from 100 K to 300 K. These results demonstrate the strong potential of AlInAsSb SAGCM APDs for eye-safe, high-sensitivity applications in LIDAR, free-space optical communication, and low-light SWIR imaging.

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AlxIn1−xAsySb1−y digital alloys on GaSb separate absorber charge multiplier avalanche photodiodes that absorb at 2-μm wavelengths have been grown with relatively thin absorber layers ranging from 50 to 400 nm. These devices exhibit extremely low room-temperature dark currents owing to the reduced narrow bandgap absorber material. Compared to previously demonstrated devices, they maintain low dark currents out to high multiplication gains. Specifically, the 100-nm absorber device exhibits a room-temperature dark current density of ∼ 35 mA/cm2 at a multiplication gain of 90, which is the lowest reported room-temperature dark current for a 2 μm absorbing III-V avalanche photodiode operating at elevated gains. As the absorber region was thinned, bulk sources of dark current were suppressed, placing an emphasis on future work to suppress surface leakage and multiplier dark currents. Adjustments to the p-type charge region were also shown to yield large dark current improvements by reducing the electric field in the narrow bandgap absorber region.

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The fast development of mid-wave infrared photonics has increased the demand for high-performance photodetectors that operate in this spectral range. However, the signal-to-noise ratio, regarded as a primary figure of merit for mid-wave infrared detection, is strongly limited by the high dark current in narrow-bandgap materials. Therefore, conventional mid-wave infrared photodetectors such as HgCdTe require cryogenic temperatures to avoid excessively high dark current. To address this challenge, we report an avalanche photodiode design using photon-trapping structures to enhance the quantum efficiency and minimize the absorber thickness to suppress the dark current. The device exhibits high quantum efficiency and dark current density that is nearly three orders of magnitude lower than that of the state-of-the-art HgCdTe avalanche photodiodes and nearly two orders lower than that of previously reported AlInAsSb avalanche photodiodes that operate at 2 µm. Additionally, the bandwidth of these avalanche photodiodes reaches ~7 GHz, and the gain–bandwidth product is over 200 GHz; both are more than four times those of previously reported 2 µm avalanche photodiodes. We demonstrate an avalanche photodiode design using photon-trapping structures to enhance the quantum efficiency and minimizing the absorber thickness, yielding high quantum efficiency, suppressed dark current density and bandwidth of ~7 GHz.

Background doping polarity type is a critical parameter for avalanche photodiode performance. We demonstrated a technique using capacitance-voltage (CV) measurements on double mesa structures with a p-i-n or n-i-p homojunctions to determine the polarity type of the unintentionally doped intrinsic (uid) region. CV measurements scale with the size of the mesa and enable design flexibility in producing variable top or bottom mesa diameters. We designed and tested AlGaAsSb and AlInAsSb structures and performed measurements at varying temperatures. Measurements varied with the top mesa, indicating the p-n junction is located between the p-region and the uid region, therefore it is n-type.

We describe the molecular beam epitaxial growth, characterization, and device performance of conventional, staircase, and photoconductive avalanche photodetectors grown with AlInAsSb digital alloys. In particular, this is the first low-noise III-V avalanche photodiode alloy family and offers the band engineering flexibility necessary to achieve staircase avalanche photodiode operation.

High-sensitivity avalanche photodiodes (APDs) are used to amplify weak optical signals in a wide range of applications, including telecommunications, data centers, spectroscopy, imaging, light detection and ranging, medical diagnostics, and quantum applications. This paper reports antimony-based separate absorption, charge, and multiplication structure APDs on InP substrates. Al0.7In0.3As0.79Sb0.21 is used for the multiplier region, and InGaAs is used as the absorber. The excess noise is comparable to that of silicon APDs; the k-value is more than one order of magnitude lower than that of APDs that use InP or InAlAs for the gain region. The external quantum efficiency without an anti-reflection coating at 1550 nm is 57%. The gradient of the temperature coefficient of avalanche breakdown voltage is 6.7 mV/K/μm, which is less than one-sixth that of InP APDs, presenting the potential to reduce the cost and complexity of receiver circuits. Semi-insulating InP substrates make high-speed operation practical for widely reported AlxIn1−xAsySb1−y-based APDs.

We have demonstrated InGaAs/AlInAsSb separate absorption, charge, and multiplication avalanche photodiodes. The multiplication gain, excess noise, and temperature-dependent dark current have been characterized. InGaAs/AlInAsSb APDs were grown on semi-insulating InP substrates, which is beneficial for bandwidth improvement compared to AlInAsSb APDs grown on GaSb substrates.

Digital alloy Al0.85Ga0.15As0.56Sb0.44, random alloy Al0.85Ga0.15As0.56Sb0.44, and random alloy Al0.79In0.21As0.74Sb0.26 are promising candidates for the multiplication regions of avalanche photodiodes (APDs) due to their low excess noise, which is comparable to that of Si APDs. The temperature dependence of avalanche breakdown in these materials has been investigated by measuring the multiplication gain. A weak temperature dependence of the breakdown voltage is observed, which is desirable to reduce the complexity of temperature or reverse bias control circuits in the optical receiver. Calculations of the alloy disorder potentials and alloy scattering rates indicate that the temperature dependence of the avalanche breakdown in these quaternary alloys is attributable to the dominance of large mass variations and high alloy scattering over phonon scattering. Impact ionization can also be impacted by the temperature dependence of the bandgap energy which affects the ionization threshold energy. Therefore, the temperature dependence of the bandgap energy has been investigated by temperature-dependent photoluminescence and external quantum efficiency measurements to further explain the temperature dependent breakdown characteristics of these materials.

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The ultra-wide bandgap of gallium oxide provides a rich plethora of electrically active defects. Understanding and controlling such defects is of crucial importance in mature device processing. Deep-level transient spectroscopy is one of the most sensitive techniques for measuring electrically active defects in semiconductors and, hence, a key technique for progress toward gallium oxide-based components, including Schottky barrier diodes and field-effect transistors. However, deep-level transient spectroscopy does not provide chemical or configurational information about the defect signature and must, therefore, be combined with other experimental techniques or theoretical modeling to gain a deeper understanding of the defect physics. Here, we discuss the current status regarding the identification of electrically active defects in beta-phase gallium oxide, as observed by deep-level transient spectroscopy and supported by first-principles defect calculations based on the density functional theory. We also discuss the coordinated use of the experiment and theory as a powerful approach for studying electrically active defects and highlight some of the interesting but challenging issues related to the characterization and control of defects in this fascinating material.

The exceptional physical properties of gallium nitride (GaN) position GaN‐based power devices as leading candidates for next‐generation high‐efficiency smart power conversion systems. However, GaN's multi‐component nature results in a high density of epitaxial defects, whereas the introduction of dielectric layers further contributes to severe interface states and dielectric traps. These factors collectively impair reliability, manifesting as threshold voltage instability and current collapse, which pose significant barriers to the advancement of GaN‐based electronics. Establishing the intrinsic relationship between device reliability and defects is crucial for understanding and addressing reliability degradation issue. Deep level transient spectroscopy (DLTS) offers valuable insights by revealing defect‐induced changes in electrical parameters during the capture and emission processes under varying biases, thereby elucidating the influence of defects from GaN buffer layers, AlGaN barriers, dielectric layer, and even at dielectric/(Al)GaN interfaces. This research aims to provide a foundational understanding of reliability degradation whereas further enabling enhancements in device performance from the perspectives of epitaxial growth and process preparation, ultimately striving to improve the reliability of GaN‐based devices and unlock their full potential for practical applications.

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This work presents an AlInAsSb-based digital alloy n-B-n extended short-wave infrared (eSWIR) detector grown by molecular beam epitaxy (MBE) on a GaSb substrate. The device achieves a 50% cutoff wavelength of ∼2.86 μm and a 100% cutoff wavelength of ∼3.5 μm at room temperature. The photodetector exhibited a specific detectivity (D∗) of 2.47 × 1010 cm·Hz1/2 ·W-1 at 300 K (with peak responsivity at 2.61 μm) at a bias voltage of -0.1 V, which improved to 1.22 × 1012 cm·Hz1/2 ·W-1 at 160 K (with peak responsivity at 2.68 μm). These results highlight the potential of AlInAsSb-based photodetectors for high sensitivity, low bias voltage operation, and compact infrared sensing systems.

We compared the photoluminescence (PL) properties of AlInAsSb digital alloy samples with different periods grown on GaSb (001) substrates by molecular beam epitaxy. Temperature-dependent S-shape behavior is observed and explained using a thermally activated redistribution model within a Gaussian distribution of localized states. There are two different mechanisms for the origin of the PL intensity quenching for the AlInAsSb digital alloy. The high-temperature activation energy E 1 is positively correlated with the interface thickness, whereas the low-temperature activation energy E 2 is negatively correlated with the interface thickness. A quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) study shows that the interface quality improves as the interface thickness increases. Our results confirm that E 1 comes from carrier trapping at a state in the InSb interface layer, while E 2 originates from the exciton binding energy due to the roughness of the AlAs interface layer.

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Quinary AlGaInAsSb avalanche photodiodes (APDs), lattice-matched to InP, were demonstrated as low-noise multiplication layers. A 995 nm thick p-i-n Al0.85Ga0.07In0.08As0.63Sb0.37 structure was grown on InP as a random alloy by molecular beam epitaxy. The devices exhibited breakdown at approximately −58 V, corresponding to a peak electric field of 628.8 kV/cm. Under 450 nm illumination, a maximum gain of 842 was achieved near breakdown with pure electron injection. Excess-noise measurements across multiple devices showed F(M) values that were reproducibly low and deviated from the McIntyre local-field prediction, remaining below those of comparable Al0.85Ga0.15As0.56Sb0.44 and Al0.79In0.21As0.74Sb0.26 APDs at moderate and high gain. At M ≈ 70, the effective k of AlGaInAsSb is approximately 0.01, compared with approximately ∼0.022 and ∼0.037 for AlGaAsSb and AlInAsSb, respectively. These results identify AlGaInAsSb as a promising quinary multiplication material for next-generation low-noise InP-based APDs and for potential application toward linear-mode single-photon detectors.

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