Avalanche Photodiodes Research Articles

Real-time LIDAR imaging by solid-state single chip beam scanner

We present a real-time light detection and ranging (LIDAR) imaging by developing a single-chip solid-state beam scanner. The beam scanner is integrated with a fully functional 32-channel optical phased array, 36 optical amplifiers, and a tunable laser at central wavelength ~1310 nm, all on a 7.5 x 3 mm^2 single chip fabricated with III-V on silicon processes. The phased array is calibrated with self-evolving genetic algorithm to enable beam forming and steering in two dimensions. Distance measurement is performed with a digital signal processing that measures the time of flight (TOF) of pulsed light with a system consisting of an avalanche photodiode (APD), trans-impedance amplifier (TIA), analog-digital converter (ADC), and a processor. The LIDAR module utilizing this system can acquire point cloud images with 120 x 20 resolution with a speed of 20 frames per seconds at a distance up to 20 meters. This work presents the first demonstration of a chip-scale LIDAR solution without any moving part or bulk external light source or amplifier, making an ultra-low cost and compact LIDAR technology a reality.

Performance analysis of an L-ary PPM MISO ground-to-satellite free-space laser link with an APD-based receiver over a Málaga turbulence channel in the presence of beam wander

In this study, the performance analysis of L -ary pulse position modulation ( L -PPM) and an avalanche photodiode (APD) receiver is investigated for a ground-station-to-low-Earth-orbit laser link. The performance is analyzed in the presence of spatial diversity in the transmitter side [i.e., a multiple-in single-out (MISO) scenario] under consideration of atmospheric turbulence and untracked beams where beam wandering effects occur. The modulated Málaga distribution is used to describe these two combined fading effects. At first, novel closed-form expressions of the probability density function and cumulative distribution function of Málaga distribution modulated by the beam wander effect in the case of MISO are deduced. We then derive an approximate expression for the upper bound of the average bit error rate (BER) in the case of L -PPM assuming a Gaussian model for the APD receiver in the presence of additive Gaussian thermal noise. The analytical expressions are verified by Monte Carlo simulations in the case of binary PPM, where the results are no longer upper bounds on the performance. Numerical results of the analytical upper-bound formula of the average BER are presented. For the system under consideration, the obtained results show that the effects of atmospheric turbulence and beam wandering for untracked beams can be effectively decreased by increasing the number of transmitters.

Mushroom mesa structure for InAlAs-InGaAs avalanche photodiodes

Mushroom mesa structure for InAlAs/InGaAs avalanche photodiodes (APD) was proposed and investigated. APD heterostructrures were grown by molecular-beam epitaxy. Fabricated APDs with the sensitive area diameter of about 30 micron were passivated by SiN deposition and demonstrated avalanche breakdown voltage Vbr 70-80 V. At the applied bias of 0.9 Vbr, the dark current was 75-200 nA. The single-mode coupled APDs demonstrated responsivity at a gain of unity higher than 0.5A/W at 1550 nm. Keywords: avalanche photodiode, InAlAs/InGaAs, mesa structure, dark current.

Germanium-on-silicon avalanche photodiode for 1550 nm weak light signal detection at room temperature

To optimize the dark current characteristic and detection efficiency of the 1550 nm weak light signal at room temperature, this work proposes a Ge-on-Si avalanche photodiode (APD) in Geiger mode, which could operate at 300 K. This lateral separate absorption charge multiplication APD shows a low breakdown voltage (Vbr) in Geiger mode of -7.42 V and low dark current of 0.096 nA at unity gain voltage (VGain=1 = -7.03 V). Combined with an RF amplifier module and counter, the detection system demonstrates a low dark count rate (DCR) of 1.1×106 counts per second and high detection efficiency η of 7.8% for 1550 nm weak coherent pulse detection at 300 K. The APD reported in this work weakens the dependence of the weak optical signal recognition on the low environment temperature and makes single-chip integration of the single-photon level detection system possible.

BER Performance of UWOC With APD Receiver in Wide Range Oceanic Turbulence

In this paper, the bit error rate (BER) performance of underwater wireless optical communication (UWOC) systems with on-off keying (OOK) modulation and an avalanche photodiode (APD) detector are analyzed in a wide range of oceanic turbulence environment, such as lognormal, Gamma, K, Weibull, and Exponentiated Weibull distributions. To achieving this goal, a new mathematical system model is established, which has not only considered the aggregated degrading phenomena, namely the absorption, scattering, and turbulence, but also been suitable for describing UWOC with APD receiver. Then the closed-form expressions of the BER performances of UWOC with APD for different turbulence distributions are derived in detail by subdividing the working situation into high and lower inter-symbol interference (ISI) scenarios. Theoretical analysis and computer simulations show that no matter what the ISI levels are, the derived closed-form expressions for system BER under various turbulences can approximate the accurate integral ones well. This is obviously helpful to the design and performance evaluation of UWOC systems.

In memoriam of E.M. Kruglov and V.V. Filimonov Quantum yield of an avalanche silicon photodiode in the 114-170 and 210-1100 nm wavelength ranges

An avalanche silicon photodiode has been developed for the near IR, visible, UV and VUV light ranges. The external quantum efficiency has been studied in the 114-170 and 210-1100 nm ranges. It has been demonstrated that the avalanche photodiode reaches the quantum yield of 29 to 9300 electrons/photon at the 160 nm wavelength and bias voltage of 190-303 V, respectively. Keywords: avalanche photodiode, vacuum ultraviolet, visible light range, near IR, silicon

Progress on photovoltaic AlGaN photodiodes for solar-blind ultraviolet photodetection

Solar-blind ultraviolet photodetectors (SBPDs) have attracted tremendous attention in the environmental, industrial, military, and biological fields. Aluminum gallium nitride (AlGaN), a kind of representative III-nitride semiconductor, has promising prospects in solar-blind photodetection owing to its tunable wide bandgap and industrial feasibility. Considering the high defect density in the AlGaN epilayer directly grown on a sapphire substrate, employing an AlN/sapphire template turns out to be an effective method to achieve a high-quality AlGaN epilayer, thereby enhancing the SBPD performances. In recent years, a variety of remarkable breakthroughs have been achieved in the SBPDs. In this paper, the progress on photovoltaic AlGaN-based SBPDs is reviewed. First, the basic physical properties of AlGaN are introduced. Then, fabrication methods and defect annihilation of the AlN/sapphire template are discussed. Various photovoltaic SBPDs are further summarized, including Schottky barrier, metal-semiconductor-metal, p-n/p-i-n and avalanche photodiodes. Furthermore, surface modification and photoelectrochemical cell techniques are introduced. Benefitting from the development of fabrication techniques and optoelectronic devices, photovoltaic AlGaN photodiodes exhibit a promising prospect in solar-blind ultraviolet photodetection.

Effect of the Thickness of the a-Si Bonding Layer at InGaAs/Si Bonded Interface on the Performance of InGaAs/Si Avalanche Photodiode

Effect of the Thickness of the a-Si Bonding Layer at InGaAs/Si Bonded Interface on the Performance of InGaAs/Si Avalanche Photodiode

Monopolarity of hot charge carrier multiplication in A-=SUP=-III-=/SUP=-B-=SUP=-V-=/SUP=- semiconductors at high electric field and noiseless avalanche photodiodes (a R e v i e w)

The results of theoretical and experimental studies of impact ionization processes and charge carrier heating in multi-valley AIIIBV semiconductors at high electric field are presented and their relationship with the features of the band structure is discussed. A role of subsidiary L- and X-valleys, complex structure of the valence band and orientation dependence of the ionization coefficients are taken into account. A new approach to the choice of semiconductor materials with a large ratio of the ionization coefficients of holes and electrons to create the noiseless avalanche photodiodes due to monopolarity of hot charge carrier multiplication is proposed. Keywords: impact ionization, multi-valley semiconductors, band structure, monopolarity of multiplication, avalanche photodiodes.

InGaAs/InAlAs SAGCMCT avalanche photodiode with high linearity and wide dynamic range

Linearity is a very important parameter to measure the performance of avalanche photodiodes (APDs) under high input optical power. In this paper, the influence of the absorption layer on the linearity of APDs is carefully studied by using bandgap engineering with the structure model of separated absorption, grading, charge, multiplication, charge, and transit (SAGCMCT). The simulated results show that in the hybrid absorption layer device structure the 1 dB compression point can be improved from -9 dBm to -2.1 dBm by increasing the proportion of the p-type absorption layer. In the device structure with only one absorption layer, increasing the doping level of the absorption layer can also improve the 1 dB compression point from -8.6 dBm to 1.43 dBm at a gain of 10. Therefore, the absorption layer is very critical for the linearity of APDs.

Local Avalanche Effect of 4H-SiC p-i-n Ultraviolet Photodiodes With Periodic Micro-Hole Arrays

In this report, 4H-SiC p-i-n photodiodes with various micro-hole arrays are fabricated, then measured and discussed by using photoelectric measurement system and simulation software. Periodic micro-hole arrays etched from p layer to i layer are obtained by using the selective etching technology, which increases the photosensitive area of devices and reduces the ultraviolet light absorption of p layer. The average dark current of devices has an ultralow value of approximate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.0\times 10 ^{-15}$ </tex-math></inline-formula> A in the low reverse bias range of 0–10 V. Furthermore, the device with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 ~\mu \text{m}$ </tex-math></inline-formula> micro-hole exhibits the best performance and its peak responsivity increased by 10.4 % compared to the conventional device. It is significant that the peak responsivity and corresponding external quantum efficiency of devices with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 ~\mu \text{m}$ </tex-math></inline-formula> micro-hole at 40 V bias are 815 % and 819 % higher than those of devices without micro-hole, respectively. This is attribute to the fact that a high electric field is observed around the micro-holes as the reverse bias increased to 40 V, which leads to local avalanche. Thus, the local avalanche photodiodes work at a relatively low bias, which improved the responsivity and quantum efficiency of the device enormously.

A Nearly Interference-Free and Depth-Resolution-Configurable Time-of-Flight System Based on a Mega-Pixel Vertical Avalanche Photodiodes CMOS Image Sensor

We present a long range (~250 m) time-of flight (TOF) system with suppressed (nearly-free) mutual-interference. The system is based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1296\times960$ </tex-math></inline-formula> pixels vertical avalanche photodiodes (VAPD) CMOS image sensor (CIS). Real-time long-range 3D-imaging with 30 fps speed (450 fps for 2D imaging) is demonstrated. Designs and operation principles of the core circuits, i.e., a photon counting circuit and a global shutter driver, are fully described. The ranging method is based on a sub-range synthesis (SRS) where a range is set by the phase of exposure pulses with respect to that of the light source of the system. The depth resolution is configurable in that the minimum sub-range width limited by the light source pulse width of 10 ns or 1.5 m can be reduced to a 10 cm by introducing an indirect-TOF operation. Furthermore, by employing a random flight timing (RFT), mutual-interference in raw signal level is suppressed by 35 dB when 2 cameras are simultaneously operated. By simulation, the present system is estimated to be tolerant up to a case of 27 cameras operation.

InGaAs/InP SAGCM avalanche photodiode with a heterojunction multiplication layer

In this paper, the InGaAs/InP separate absorption, grading, charge, and multiplication avalanche photodiode (SAGCM-APD) with a heterojunction multiplication layer and a hybrid absorption layer has been simulated. Due to the effect of the heterojunction multiplication layer on avalanche photodiode collision ionization, compared with the traditional structure, the break-down voltage and the punch-through voltage of the structure with a heterojunction multiplication layer was reduced by 2 V. By optimizing the thickness of the heterojunction multiplication layer, the electrical performance of the device has been enhanced. The avalanche gain was 193.37, which is much higher than the conventional structure (51.65). Besides, the thickness of InP in the heterojunction multiplication layer affects the capacitance characteristics of the device.

Investigation of the zinc diffusion process into epitaxial layers of indium phosphide and indium-gallium arsenide grown by molecular beam epitaxy

The results of an investigation of the peculiarities of the zinc diffusion process into epitaxial layers of indium phosphide and indium-gallium arsenide aimed at the fabrication of an avalanche photodiode for a single-photon detector are presented. The diffusion of zinc into indium phosphide through an intermediate layer of indium-gallium arsenide ensures better surface quality compared with the direct diffusion of zinc into the indium phosphide layer. We discovered that systems such as a quartz reactor with resistive heating with an internal solid-state source of zinc vapor and the reactor of a metal-organic chemical vapor deposition setup with hydrogen as a carrier gas make it possible to achieve similar concentrations of doping p-type impurity, which exceed 2×1018cm−3. The depth of zinc diffusion in the indium phosphide layer ranged from 2 to 3.5 µm, depending on the temperature and duration of the diffusion process. Such depths are required for fabrication of effective avalanche photodiodes.

Low-cost laser diode pulse generator for quantum information applications

A simple short-pulse generator circuit based on electronic gates is designed for short electric pulse of about 12 ns at Full Width at Half Maximum (FWHM) and 3.6 Volt amplitude for driving a laser diode. Using our circuit with a 780 nm laser diode designed and fabricated for producing short light pulses. The circuit utilizes an AND gate, a XOR gate, and a common function generator, provides a repetition rate from DC up to 1 MHz. The laser pulses were generated and then detected via an avalanche photodiodes (APD). This finding can benefit the field of light-based quantum information including single photon experiments.

Investigation of the parameters of a single photon detector for quantum communication

Nowadays the best single photon detectors from a practical view are those based on InGaAs/InP avalanche photodiodes, operating at a wavelength of 1.55 μm. The dependence of quantum efficiency and noise levels on the temperature and bias voltage of avalanche photodiodes were carried out.

A Mechanically Flexible, Implantable Neural Interface for Computational Imaging and Optogenetic Stimulation Over 5.4×5.4mm2 FoV.

Emerging optical functional imaging and optogenetics are among the most promising approaches in neuroscience to study neuronal circuits. Combining both methods into a single implantable device enables all-optical neural interrogation with immediate applications in freely-behaving animal studies. In this paper, we demonstrate such a device capable of optical neural recording and stimulation over large cortical areas. This implantable surface device exploits lens-less computational imaging and a novel packaging scheme to achieve an ultra-thin (250μm-thick), mechanically flexible form factor. The core of this device is a custom-designed CMOS integrated circuit containing a 160×160 array of time-gated single-photon avalanche photodiodes (SPAD) for low-light intensity imaging and an interspersed array of dual-color (blue and green) flip-chip bonded micro-LED (μLED) as light sources. We achieved 60μm lateral imaging resolution and 0.2mm3 volumetric precision for optogenetics over a 5.4×5.4mm2 field of view (FoV). The device achieves a 125-fps frame-rate and consumes 40 mW of total power.

High-performance HgCdTe avalanche photodetector enabled with suppression of band-to-band tunneling effect in mid-wavelength infrared

HgCdTe avalanche photodiodes promise various fascinating applications due to the outstanding capability of detecting weak signals or even single photon. However, the underlying transport mechanisms of diverse dark current components are still unresolved at high reverse bias, thus limiting the development of high-performance devices. Here, we establish an accurate model to demonstrate the competitive mechanism between band-to-band and avalanche dark currents in positive-intrinsic-negative structures. Based on the high consistency between the simulated and measured results, we find that both components jointly dominate overall dark current but with a larger avalanche current. This breaks the conventional cognition that band-to-band dark current contributes the majority. With the guidance, we reconstruct an optimized device and achieve gain 1876 (6153) and dark current 10−10 (10−9) A at bias −10 (−10.5) V, respectively. Comparisons of dark current and gain with reported single-element devices further confirm the outstanding performance of our device.

Optimized Selective‐Area p‐Type Diffusion for the Back‐Illuminated Planar InGaAs/InP Avalanche Photodiodes by a Single Diffusion Process

Herein, an alternative approach of selective‐area zinc diffusion technique by single rapid thermal diffusion (RTD) using a Zn3P2/Zn/SiO2 multilayer structure is proposed to realize p‐type doping in the InP cap so as to fabricate planar InGaAs/InP avalanche photodiodes (APDs). Through the optimization of selective‐area zinc diffusion in the InP cap, a low dark current, high responsivity, fast transient response, and high reliability near‐infrared back‐illuminated planar InGaAs/InP APD is obtained, which demonstrates a simple and efficient method for the development of high‐performance planar InGaAs/InP APD focal plane arrays.

Secondary scintillation yield in pure krypton

The absolute secondary scintillation yield is of paramount importance for modelling dual-phase or high-pressure gas detectors, to be used in contemporary and in future rare event detection experiments. In addition, the search for neutrinoless double electron capture complements the search for neutrinoless double beta decay and has been measured for 124Xe in several Dark Matter and Double Beta decay detectors, operating at present. Krypton presents itself as an interesting candidate for double electron capture detection experiments. We have studied the krypton secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap. A large area avalanche photodiode has been used to allow the simultaneous detection of the scintillation pulses as well as the direct interaction of x-rays, the latter being used as a reference for the calculation of the number of charge carriers produced by the scintillation pulses and, thus, the determination of the number of photons impinging the photodiode. An amplification parameter of 113 photons per kV per drifting electron and a scintillation threshold of 2.7 Td (0.7 kVcm−1bar−1 at 293 K) was obtained, in good agreement with the simulation data reported in the literature. On the other hand, the ionisation threshold in krypton was found to be around 13.5 Td (3.4 kVcm−1bar−1), less than what had been obtained by the most recent simulation work-package. The krypton amplification parameter is about 80% and 140% of those measured for xenon and argon, respectively.