Avalanche Photodiodes Research Articles

A fully functional palmtop microchip electrophoresis analyzer with laser-induced fluorescence detection

Microchip electrophoresis (MCE) is an ideal tool for rapid on-site analysis of multiple components, therefore the demand for portable MCE devices is increasing. In this work, a fully functional palmtop MCE analyzer was built, integrating units of sample injection, laser-induced fluorescence (LIF) detection, high-voltage (HV), imaging and data acquisition. Frames were fabricated with 3D printing to encapsulate miniaturized components selected with balanced consideration on size, cost and performance. The LIF unit contains a laser diode as the excitation light source, a collimating lens used in the commercial laser diode as the focusing lens and an avalanche photodiode (APD) for the laser distance meter as the photoelectric converter. The sample injection was achieved by negative pressure induced pinching. The total cost of the device is approximately $600 with a size of 89 × 98 × 98 mm3 and a weight of 350 g. It can be powered by a laptop or a mobile power bank. The limit of detection (LOD) measured under a typical MCE condition for sodium fluorescein could be 110 pM. The applicability of the device was demonstrated with the detection of rhodamines and DNA fragments.

Free-Space Optical Data Receivers with Avalanche Detectors for Satellite Downlinks Regarding Background Light.

Data receiving frontends using avalanche photodiodes are used in optical free-space communications for their effective sensitivity, large detection area, and uncomplex operation. Precise control of the high voltage necessary to trigger the avalanche effect inside the photodiode depends on the semiconductor’s excess noise factor, temperature, received signal power, background light, and also the subsequent thermal noise behavior of the transimpedance amplifier. Several prerequisites must be regarded and are explained in this document. We focus on the application of using avalanche photodiodes as data receivers for the on/off-keying of modulated bit streams with a 50% duty cycle. Also, experimental verification of the performance of the receiver with background light is demonstrated.

Measurement of focal light spot at single-photon level with silicon photomultipliers

Focal spot (light spot) at single-photon level have important applications in many fields. This report demonstrates a method for measuring focal spot size at the single-photon level indirectly. This method utilizes Silicon Photomultiplier (SiPM) as the single-photon sensitive detectors, combined with a nano-positioning stage. The approach involves one- or two-dimensional space scanning and a deconvolution operation, which enable evaluations of the size and spatial distribution of the focal spot formed by a single-photon-level pulsed laser. The results indicate that the average full width at half maximum of the focal spot is about 0.657 μm, which is close to the nominal resolution of the objective lens of the microscope (i.e. 0.42 μm). The proposed method has two key advantages: (1) it can measure focal spot at the single-photon level, and (2) the focal spot can easily be aligned with the detector because the array area of the Geiger mode avalanche photodiode (Gm-APD) cells in SiPM is usually on the order of square millimeter, and there is no need to put an optical slit, knife edge, or pinhole in front of the detector. The method described herein is applicable in weak focal spot detection related fields.

Dark Current and Gain Modeling of Mid-Wave and Short-Wave Infrared Compositionally Graded HgCdTe Avalanche Photodiodes

We present a detailed methodology for drift-diffusion (DD) modeling of gain and dark currents in mid-wave infrared (MWIR) and short-wave infrared (SWIR) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {Hg}}_{{1}-{x}}$ </tex-math></inline-formula> Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Te <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-around-n</i> avalanche photodiodes (APDs) based on a comprehensive analysis of experimentally obtained data from three different sets of devices. These devices are fabricated on homogeneous and compositionally-graded films with cadmium composition ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}\,\,=0.37$ </tex-math></inline-formula> to 0.45, each with differing geometrical dimensions, and tested at operating temperatures ranging from 140 to 240 K. The temperature, composition, and electric-field dependent impact ionization (ImI) coefficients are calibrated first according to the given experimental gain data. The gain-normalized dark current (GNDC) curve, along with the presumption of electron-only multiplication, is then used to thoroughly understand and model the behavior of diffusion and generation currents. At high biases, the GNDC curve reveals contributions from tunneling, which are classified as either trap-assisted or band-to-band based on their temperature dependence. The tunneling mechanisms are modeled accordingly: trap-assisted tunneling (TAT) is scaled inversely with Shockley–Read–Hall (SRH) lifetime, while band-to-band tunneling (BTBT) is scaled with bandgap, effective mass, and an additional empirical temperature term. Finally, the comprehensive model is applied to all three experimental devices across the operating temperature range with good agreement.

Demonstration of a Solar-Blind Single-Photon Imaging Lidar Based on SiC Ultraviolet Avalanche Photodiodes

In this work, a prototype solar-blind single-photon imaging lidar based on SiC ultraviolet (UV) avalanche photodiodes (APD) is demonstrated. The SiC APD with a peak responsivity at ~280 nm can greatly lessen the strict solar-blind filtering requirement for the system. When characterized by using a gated quenching circuit, the SiC APD operating in Geiger mode could exhibit a room temperature single photon detection efficiency of ~27% with a dark count probability of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.59\times 10 ^{-2}$ </tex-math></inline-formula> . Based on the SiC APD, a 266 nm nanosecond pulsed laser, a galvanometer scanner and a time-correlated single-photon counter, 3-dimensional depth image with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$128\times 128$ </tex-math></inline-formula> resolution is realized by the prototype system in daylight. The average ranging accuracy of the system is found within 28 mm based on current setup.

Material Defects and Dark Currents in InGaAs/InP Avalanche Photodiode Devices

An In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/indium phosphide (InP) avalanche photodiode (APD) with a separate absorption, grading, charge, and multiplication (SAGCM) structure is epitaxially grown by molecular beam epitaxy (MBE). The resulting material is studied using X-ray diffraction (XRD), photoluminescence (PL), and scanning transmission electron microscopy. The activation energy extracted from the dark current of the APD indicates that it is dominated by the generation–recombination (G–R) process. Deep low-temperature PL peaks reveal the existence of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{v} + 0.42$ </tex-math></inline-formula> -eV deep energy level defect in the indium–gallium–arsenide (InGaAs) absorber layer, which is considered to be a result of point defects caused by Ga-poor or In-poor MBE growth conditions. The effect of the defect on the dark current is confirmed using numerical calculation methods.

Long-Distance Vehicle Dynamic Detection and Positioning Based on Gm-APD Lidar and LIDAR-YOLO

Aiming at the problems of long-distance night dynamic object detection in military operations, such as difficult imaging of traditional equipment, a small number of object pixels, a large difference in object size at different distances, and poor real-time performance. A long-distance vehicle detection method based on the LIDAR-YOLO network for Gm-APD (Geiger mode avalanche photodiode) lidar image is proposed. This method is improved based on YOLOv5s, which can detect long-distance vehicles and accurately locate motion trajectories in real-time. Firstly, the intensity image I of the lidar is preprocessed and combined with the distance image R, the BC_IIR image is obtained, and the vehicle detection data set is established. Then, according to the obvious vehicle features in the BC_IIR image, the low-complexity backbone network LIDARNet is redesigned, and several attention mechanism modules are added. The network feature extraction ability is enhanced by comparing and selecting the CA attention mechanism module. In the network prediction layer, context-aware feature map fusion is added to improve the detection precision of vehicles at different distances. Next, a GIOU loss is introduced to improve the detection precision of occluded vehicles. Finally, the method can depict the trajectory of the vehicle in 3D space based on distance information. After testing, the network achieves a detection speed of 62.67 frames per second (FPS), recall rate (R) = 98.19%, precision rate (P) = 95.53%, and F1 is 0.9675. The results show that the algorithm has better performance than other methods.

Determination of the background doping polarity for unintentionally doped AlGaAsSb and AlInAsSb avalanche photodiodes on InP substrates

Background doping polarity is a critical design parameter for the performance of many optoelectronic devices, including avalanche photodiodes. We have applied a technique by using capacitance–voltage (CV) measurements on double mesa structures with a p-i-n or n-i-p homojunction to determine the background polarity type of the unintentionally doped intrinsic region. Because CV measurements scale with the size of the mesa, they support design flexibility in producing variable-sized top and bottom mesa diameters. In this work, we grew, fabricated, and tested AlGaAsSb and AlInAsSb random alloy double mesa p-i-n structures and undertook CV measurements at 295, 150, and 77 K. It was found that the capacitance varied with the top mesa diameter for both material systems, and not the bottom mesa diameter, indicating that the unintentionally doped intrinsic region is n-type in nature.

An Optoelectronic Transimpedance Amplifier in 180-nm CMOS for Short-range LiDAR Sensors

This paper presents an optoelectronic transimpedance amplifier (OTIA) implemented in a 180-nm CMOS technology, in which a PSUP+/SUP/N-well avalanche photodiode (APD) is realized on-chip to reduce signal distortions occurring from bond-wire and I/O pad at the input node, a voltage-mode feedforward input configuration is exploited to boost the transimpedance gain, and a cross-coupled inverter-based post-amplifier (CI-PA) is added to reduce the mismatches from the previous stage. The proposed OTIA demonstrate 95.1-dBΩ transimpedance gain, 608-MHz bandwidth, 4.54-pA/√Hz noise current spectral density, 26.4-dB dynamic range that corresponds to the input currents of 2.38 μASUBpp/SUB ~ 50 μASUBpp/SUB, and 39.3-mW power dissipation from a single 1.8-V supply. The chip core occupies the area of 0.068 ㎟.

Modeling Approaches for Gain, Noise and Time Response of Avalanche Photodiodes for X-Rays Detection

We report on a suite of modeling approaches for the optimization of Avalanche Photodiodes for X-rays detection. Gain and excess noise are computed efficiently using a non-local/history dependent model that has been validated against full-band Monte Carlo simulations. The (stochastic) response of the detector to photon pulses is computed using an improved Random-Path-Length algorithm. As case studies, we consider diodes consisting of AlGaAs/GaAs multi-layers with separated absorption and multiplication regions. A superlattice creating a staircase conduction band structure is employed in the multiplication region to keep the multiplication noise low. Gain and excess noise have been measured in devices fabricated with such structure and successfully compared with the developed models.

Upgrade of the CMS Barrel Electromagnetic Calorimeter for the High Luminosity LHC

The high luminosity upgrade of the LHC (HL-LHC) at CERN will provide unprecedented instantaneous and integrated luminosities of up to 7.5×1034 cm−2s−1 and 4500 fb−1, respectively, from 2029 onwards. To cope with the extreme conditions of up to 200 collisions per bunch crossing, and increased data rates, the on- and off-detector electronics of the CMS electromagnetic calorimeter (ECAL) will be replaced. A dual gain trans-impedance amplifier and an ASIC providing two 160 MHz ADC channels, gain selection, and data compression will be used. The lead tungstate crystals and avalanche photodiodes (APDs) in the current ECAL will keep performing well and will therefore be maintained. The noise increase in the APDs, due to radiation-induced dark currents, will be minimised by reducing the ECAL operating temperature from 18 °C to around 9 °C. Prototype HL-LHC electronics have been tested and have shown promising results. In two test beam periods using the CERN SPS H4 beamline and an electron beam, the new electronics achieved the target energy resolution and a timing resolution consistent that is consistent with our requirements of 30 ps timing for energies greater than 50 GeV.

Quantum non-Gaussianity certification of photon number-resolving detectors.

We report on direct experimental certification of the quantum non-Gaussian character of a photon number-resolving detector. The certification protocol is based on an adaptation of the existing quantum non-Gaussianity criteria for quantum states to quantum measurements. In our approach, it suffices to probe the detector with a vacuum state and two different thermal states to test its quantum non-Gaussianity. The certification is experimentally demonstrated for the detector formed by a spatially multiplexed array of ten single-photon avalanche photodiodes. We confirm the quantum non-Gaussianity of POVM elements Π^m associated with the m-fold coincidence counts, up to m = 7. The experimental ability to certify from the first principles the quantum non-Gaussian character of Π^m is for large m limited by low probability of the measurement outcomes, especially for vacuum input state. We find that the injection of independent Gaussian background noise into the detector can be helpful and may reduce the measurement time required for reliable confirmation of quantum non-Gaussianity. In addition, we modified and experimentally verified the quantum non-Gaussianity certification protocol employing a third thermal state instead of a vacuum to speed up the whole measurement. Our findings demonstrate the existence of efficient tools for the practical characterization of fundamental non-classical properties and benchmarking of complex optical quantum detectors.

Photomechanical detection of bioaerosol fluorescence free-from solar background

Detection of biological molecules in aerosol via fluorescence signature is well established. However, standoff detection of weak target fluorescence deeply submerged in the ambient bright solar background is challenging with conventional approaches (using photo-multiplier tubes, avalanche photodiodes or ICCD) due to saturation effects and overlapping spectral signatures. Here, we demonstrate a Quartz tuning fork (QTF) enhanced photomechanical detection of fluorescence spectra from bio-aerosols free from broadband solar light. The detection is based on resonant excitation of QTF at 32.78 kHz by on–off modulated laser-induced fluorescence from aerosol while the stray solar background is essentially suppressed by the QTF. A remote detection of fluorescence spectra of Bacillus Globbigi and Riboflavin aerosols was demonstrated at 5 m standoff distance using two near-UV excitation wavelengths with good signal-to-noise ratio. The fluorescence signal increases linearly with excitation power, concentration and quality factor of the QTF. Besides being low-cost and reliable, the detection range of the presented approach can be extended to large standoff distance free-from ambient sunlight noise.

A High Time-Resolved Front-End ASIC for APD Array Detector in Nuclear Resonant Scattering Experiments With Synchrotron Radiation

A high time-resolved front-end readout chip has been developed for avalanche-photodiode (APD) array detectors in nuclear resonant scattering (NRS) experiments. The chip has eight channels. Each channel consists of a preamplifier, a voltage discriminator, an open-drain output driver, and a local digital-to-analog converter (LDAC). The application-specific integrated circuit (ASIC) chip has been designed and fabricated in a 0.13- <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> CMOS technology with a chip size of 1.1 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2.3$ </tex-math></inline-formula> mm. The electrical characterizations of all eight channels demonstrate good time resolution (TR) (rms) on the output pulse leading edge, with the measurement result better than 25 ps for high input signal charges (>30 fC) and better than 98 ps for low input signal charges (8–30 fC), for an APD sensor capacitance as large as 15 pF. The equivalent noise charge (ENC) received from the measurement can be represented as ENC = 592.4 e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> + 50.7 e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> /pF. The power consumption is 17.6 mW per channel: 2.7 mW for the preamplifier–discriminator stage and 14.9 mW for the output low-voltage differential signaling (LVDS) driver.

Area-dependent gain and noise characteristics of mid-wavelength infrared HgCdTe planar electron avalanche photodiodes

This paper mainly investigates the area-dependent gain and noise characteristics of mid-wavelength infrared (MWIR) Hg0.7Cd0.3Te planarelectron avalanche photodiodes (e-APDs) operated at 80 K. The 10-μm-radius diode exhibits low dark current in the magnitude of 10–13 A below −5.5 V, high gain up to 1270 at −10 V, and low excess noise factor between 1 and 1.2. The optimal performances are compromised by tunneling current, which should be further suppressed. Studies on variable-area diodes show that larger diodes have a reduced gain due to a smaller contribution from edge gain, as well as an increased 1/f noise and corner frequency due to higher defect density. From the gain and noise perspectives, HgCdTe e-APDs with smaller junction areas are more suitable for focal plane array (FPA) applications.

Digital single-photon-avalanche-diode arrays for time-of-flight Thomson scattering diagnostics.

The collection optics of Thomson scattering systems for plasma devices are designed with maximum possible étendue to keep the required laser energy low. If the spatial resolution along the laser beam is performed by a time-of-flight method, then the detectors, in addition to a large sensitive area, must offer a high frequency bandwidth. Up until now, only microchannel-plate photomultipliers meet these requirements. Here, we investigate the potential use of digital avalanche photodiode arrays operated in the Geiger mode as alternative detectors. In this mode of operation, each array will serve as a fast, sensitive detector. The use of these detectors will lead to significant improvements of the Thomson scattering diagnostic. Most important of these will be a better spatial resolution, down to about 2cm without deconvolution. Furthermore, the lifetime of the detectors will be increased; the detectors will cover the whole blue wing of the scattered spectrum when using a single wavelength laser, and this will enable measurements of electron temperature and density profiles at kHz repetition rates.

Linear Mode Avalanche Photodiodes With Antimonide Multipliers on InP Substrates

We provide an overview of our progress on the development of linear mode avalanche photodiodes (LmAPDs) on InP substrates using antimony (Sb)-based multipliers for short-wavelength infrared (SWIR) spectral region. We identify the key figures of merit of LmAPDs to provide higher sensitivity and speed for applications like light detection and ranging (LiDAR) and remote sensing. We discuss the design of separate absorption, charge, and multiplication (SACM) APDs that are used for narrow gap absorption. We summarize our results on the impact ionization, multiplication gain, dark current, and excess noise of AlGaAsSb and AlInAsSb multipliers lattice-matched to InP substrates. Finally, we identify the key technical challenges associated with the development of SACM APDs on InP substrates.

Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction

Germanium-on-silicon (Ge-on-Si) avalanche photodiodes (APDs) are widely used in near-infrared detection, laser ranging, free space communication, quantum communication, and other fields. However, the existence of lattice defects at the Ge/Si interface causes a high dark current in the Ge-on-Si APD, degrading the device sensitivity and also increasing energy consumption in integrated circuits. In this work, we propose a novel surface illuminated Ge-on-Si APD architecture with three terminals. Besides two electrodes on Si substrates, a third electrode is designed for Ge to regulate the control current and bandwidth, achieving multiple outputs of a single device and reducing the dark current of the device. When the voltage on Ge is − 27.5 V , the proposed device achieves a dark current of 100 nA, responsivity of 9.97 A/W at − 40 dBm input laser power at 1550 nm, and optimal bandwidth of 142 MHz. The low dark current and improved responsivity can meet the requirements of autonomous driving and other applications demanding weak light detection.

Zn diffusion depth effect on photoresponse uniformity in InP/InGaAs avalanche photodiodes

Numerical simulation of the electric field distribution and photocurrent response of a planar InP/InGaAs avalanche photodiode is presented for small variations of the multiplication width. The Zn dopant diffusion front is obtained by numerically simulating the diffusion process. The simulation results indicate that while a local peak value of the electric field is observed near the device edge, it is not associated with a significant increase in the photocurrent response. Experimental photocurrent mapping of an avalanche photodiode shows a response at the edge that is enhanced by ~ 60% compared to the centre response. Scanning electron microscope images of Zn diffused structures show that the depth is enhanced by 0.03 m at the edge, compared to the centre. Simulations of devices with varied multiplication width show that the magnitude of the increase in photocurrent expected for the observed depth enhancement is consistent with the observed photocurrent enhancement along the edge the active device.

Performance analysis of near-earth, lunar and interplanetary optical communication links

The performance of near-Earth, lunar and interplanetary laser optical communications is investigated by using simulation models which were successfully verified in previous projects. The simulation models consider typical mission design parameters like transmit power and operation wavelength for the optical laser transmitters, different apertures of the optical telescope, varying distances between the Earth ground station and the spacecraft terminals, Geiger-mode avalanche photodiodes (APD) or superconducting nanowire single photon detection (SNSPD) receivers, atmospheric disturbances like scintillation and absorption, background noises for the uplink and downlink and appropriate pulse position modulation (PPM) orders. Typical design parameters are those of published ESA (European Space Agency) and NASA (National Aeronautics and Space Administration) missions. The investigations of laser optical communications for various system parameters and different distances between the Earth ground station and the spacecraft could also help to achieve an overview of free space and deep space optical communications for different orbit constellations for future missions with laser optical communication links.