Edge Breakdown Research Articles

Impact of overvoltage on the mode transition of the spark gap switch: from edge breakdown to stochastic breakdown

Impact of overvoltage on the mode transition of the spark gap switch: from edge breakdown to stochastic breakdown

Low breakdown voltage and CMOS compatible avalanche photodiode based on SOI substrate.

In this work, we present a novel, to the best of our knowledge, lateral avalanche photodiode (APD) with low breakdown voltage and high bandwidth which has the potential to serve as a core device in future large-scale advanced optoelectronic hybrid chips. By taking advantage of a silicon-on-insulator (SOI) substrate combined with a separation absorption multiplier (SAM) structure, the demonstrated APDs exhibit a high gain of 148. Furthermore, the minimum breakdown voltage of the measured device is 6.1 V, which represents the lowest breakdown voltage for Si-APD, making it compatible with the existing CMOS technology for low voltage operation. Benefiting from an ultra-thin top silicon and lateral SAM structure, the problem of edge breakdown has been completely solved. Additionally, a set of device arrays with absorption and avalanche regions of different sizes is also manufactured and compared. Our findings indicate that the proposed APD has fascinating application prospects in the CMOS process-based LIDAR chips.

Investigation of a rotating stall in a supercritical CO2 centrifugal compressor

Due to the nonlinear behavior of carbon dioxide properties at its critical point and the size effect of the supercritical carbon dioxide (S-CO2) centrifugal compressor, the stall causation mechanism differs between the S-CO2 centrifugal compressor and a conventional air compressor. The comprehension of the induced principle of the S-CO2 compressor rotating stall holds immense significance in enhancing stall margin and efficiency. This paper employs unsteady simulations to investigate the causes of the impeller rotating stall in the S-CO2 centrifugal compressor. The results show that the leading edge breakdown vortex (LEBV) formed by the tip leakage vortex (TLV) breakdown and the reverse flow in the passage are the reasons for blocking the passage and ultimately causing the rotating stall of the impeller. The migration motion of the LEBV not only induces the leading edge spillage phenomenon but also influences the intensity of the tip leakage flow (TLF) in adjacent passages, causing the propagation of the TLV breakdown phenomenon in the opposite direction to that of impeller rotation. The TLV undergoes intermittent breakdown in flow field, which is influenced by variations in TLF intensity. Additionally, there is a preceding process of breakdown-induced vortex formation and disappearance prior to TLV fragmentation.

The influence of the structure of guard rings on the dark currents of silicon p-i-n photodiodes

The article examines the influence of the guard rings (GR) system structure on the dark currents of responsive elements (RE) and the actual guard rings of silicon 4-element p-i-n photodiodes (PD). The samples were made on the basis of p-silicon by planar technology. Samples with one, two, and three GR were produced. It was found that increasing the amount of n+-GRs does not reduce the dark current of the REs. But with an increase in the number of n+-GRs, the probability of an edge breakdown of the n+-p-junction in the regions of the exit of the hetero-junction of the GR to the surface increases. It is possible to reduce the levels of dark current of REs and GR by combining n+- and p+- guard regions, where p+-GR is a region of restriction of dark current leakage channels, isotypic with the substrate material. PD was made with p+-GR on the periphery of the crystal in the form of a concentric ring, as well as with a p+- region on the entire periphery of the crystal. This makes it possible to reduce the level of of dark current of n+- GR due to the reduction of the area of collection of charge carriers from the surface. But a significant decrease in the dark current of REs was not observed in such cases. We proposed to carry out boron diffusion in the gaps between REs and between REs and n+-GR.

A 3.06 μm Single-Photon Avalanche Diode Pixel with Embedded Metal Contact and Power Grid on Deep Trench Pixel Isolation for High-Resolution Photon Counting.

In this study, a 3.06 μm pitch single-photon avalanche diode (SPAD) pixel with an embedded metal contact and power grid on two-step deep trench isolation in the pixel is presented. The embedded metal contact can suppress edge breakdown and reduce the dark count rate to 15.8 cps with the optimized potential design. The embedded metal for the contact is also used as an optical shield and a low crosstalk probability of 0.4% is achieved, while the photon detection efficiency is as high as 57%. In addition, the integration of a power grid and the polysilicon resistor on SPAD pixels can help to reduce the voltage drop in anode power supply and reduce the power consumption with SPAD multiplication, respectively, in a large SPAD pixel array for a high-resolution photon-counting image sensor.

Planar InAlAs/InGaAs avalanche photodiode with 360 GHz gain×bandwidth product

This paper describes a guardring-free planar InAlAs/InGaAs avalanche photodiode (APD) by computational simulations and experimental results. The APD adopts the structure of separate absorption, charge, and multiplication (SACM) with top-illuminated. Computational simulations demonstrate how edge breakdown effect is suppressed in the guardring-free structure. The fabricated APD experiment results show that it can obtain a very low dark current while achieving a high gain×bandwidth (GB) product. The dark current is 3 nA at 0.9V br, and the unit responsivity is 0.4 A/W. The maximum 3 dB bandwidth of 24 GHz and a GB product of 360 GHz are achieved for the fabricated APD operating at 1.55 μm.

A Current-Mode Optoelectronic Receiver IC for Short-Range LiDAR Sensors in 180 nm CMOS

This paper presents three different types of on-chip avalanche photodiodes (APDs) realized in a TSMC 180 nm 1P6M RF CMOS process, i.e., a P+/N-well (NW) APD for its high responsivity and large bandwidth by excluding slow diffusion currents; a P+/Deep N-well (DNW) APD for its improved near-infrared (NIR) sensitivity; and a P+/NW/DNW APD for its capability to prevent premature edge breakdown and improve NIR sensitivity. Thereafter, a conventional voltage-mode optoelectronic receiver (V-OER) was realized to confirm the feasibility of the three on-chip APDs. However, the measured results of the V-OER demonstrate a very narrow dynamic range. Therefore, we propose a current-mode optoelectronic receiver (C-OER) realized in the same CMOS process for the applications of short-range LiDAR sensors, where current-conveyor input buffers are exploited to deliver the photocurrents with no significant signal loss to the following inverter cascode transimpedance amplifier, hence resulting in an extended dynamic range. The optically measured results of the C-OER with an 850 nm laser source demonstrate large output pulses. The C-OER chip consumes 47.8 mW from a 1.8 V supply and the core occupies 0.087 mm2.

Avalanche Photodiodes and Silicon Photomultipliers of Non-Planar Designs

Conventional designs of an avalanche photodiode (APD) have been based on a planar p–n junction since the 1960s. APD developments have been driven by the necessity to provide a uniform electric field over the active junction area and to prevent edge breakdown by special measures. Most modern silicon photomultipliers (SiPM) are designed as an array of Geiger-mode APD cells based on planar p–n junctions. However, the planar design faces an inherent trade-off between photon detection efficiency and dynamic range due to loss of an active area at the cell edges. Non-planar designs of APDs and SiPMs have also been known since the development of spherical APDs (1968), metal-resistor-semiconductor APDs (1989), and micro-well APDs (2005). The recent development of tip avalanche photodiodes (2020) based on the spherical p–n junction eliminates the trade-off, outperforms the planar SiPMs in the photon detection efficiency, and opens new opportunities for SiPM improvements. Furthermore, the latest developments in APDs based on electric field-line crowding and charge-focusing topology with quasi-spherical p–n junctions (2019–2023) show promising functionality in linear and Geiger operating modes. This paper presents an overview of designs and performances of non-planar APDs and SiPMs.

Dual Dynamic Programming for the Mean Standard Deviation Canadian Traveller Problem

This article studies the mean standard deviation (mean-std) Canadian traveller problem (CTP). Different from the canonical CTP, which aims at minimizing the traveller's expected travel time, while considering edge breakdown probabilities, we introduce the reliability version of CTP, which tries to find a routing policy with the minimal linear combination of the travel time's mean and standard deviation. With the recent development of internet-of-things (IoT) technology, the transportation network's edges' travel-time statistics, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> . <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</i> ., mean and standard deviation, as well as the traversal probabilities, are available to the end users. With those information, we propose a dual dynamic programming (DDP) method, which simultaneously estimates the first-order and the second-order moments of a given decision-list (DL) policy, and thereby makes improvements towards to the optimal one through the generalized policy iteration (GPI) scheme. We construct an open source benchmark environment to evaluate the performance of different mean-std CTP solutions, and show that the DDP method outperforms state of the arts in a range of transportation networks.

Tip Avalanche Photodiode—A spherical-junction SiPM concept

An avalanche region of APD cells in modern SiPMs is formed by a planar p–n junction, where an edge breakdown is suppressed by area-consuming measures. Performance of the planar SiPMs is limited by an inherent trade-off between photon detection efficiency (PDE) affected by an inactive cell area and dynamic range dependent on the cell pitch and capacitance. To overcome the limitations of the planar SiPM design, a spherical-junction-based SiPM – Tip Avalanche Photodiode (TAPD) – has recently been developed. Its quasi-spherical tips turn the edge breakdown problem into benefits of highly efficient collection and multiplication of photoelectrons in focusing electric field, low breakdown voltage, low cell capacitance, and eliminate needs in the separation borders between the APD cells. TAPD samples of 15 um pitch outperform the state-of-the-art SiPMs in the record PDE of 73% at the peak sensitivity wavelength of 608 nm. Moreover, the PDE is above 45% in a range of 400 to 800 nm and 22% at 905 nm. The high PDE is accompanied by the fast single electron response and cell recovery time of about 4 ns due to the low capacitance of the tips. The report presents an overview of the spherical-junction-based APD and SiPM designs and features.

Junction Engineering-Based Modeling and Optimization of Deep Junction Silicon Single-Photon Avalanche Diodes for Device Scaling

A silicon single-photon avalanche diode (Si-SPAD) with a deep multiplication zone was fabricated using 0.11- <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. Deep n-well (DNW) implantation with three energy levels was performed to prepare a deep junction, and the highest breakdown voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {BR}}$ </tex-math></inline-formula> ) and lowest dark count rate (DCR) were obtained at the highest DNW implantation energy. In addition, devices with different structures were manufactured: a shallow junction, deep junction with mask DNW, deep junction with mask DNW without shallow trench isolation (STI), and deep junction with blank DNW. The blank DNW structure exhibited a lower edge breakdown risk and less deviation between samples compared to those of mask DNW structure in terms of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {BR}}$ </tex-math></inline-formula> and DCR. Moreover, a new edge breakdown risk was observed between DNW and p-well (PW) in the DNW blank structure, which could be alleviated by adjusting the PW sizes. According to the measurement results, the STI structure was preferable in terms of fill factor. Measurements were obtained from real fabricated test device structures, and technology computer-aided design (TCAD) for various factors associated with Si-SPADs with deep multiplication structures was performed.

High-Performance Lateral Avalanche Photodiode Based on Silicon-on-Insulator Structure

In this work, a silicon-on-insulator (SOI)-based lateral avalanche photodiode (APD) is proposed and fabricated. The device features lateral separate-absorption-multiplication (SAM) and electron-only injection. The bandwidth is optimized with the effective blocking of the deep photogenerated carriers by SOI structure. The device stability is also improved by additional shallow P-well region near the N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -region which can eliminate the edge breakdown induced by the curvature effect. Simulation results demonstrate that avalanche region (high electric field zone) is confined at the lateral PN <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> junction. Experimental fabrication and characterizations are further realized, and this SOI-based lateral APD device exhibits high responsivity (1.92 A/W at 7.8 V for 300 nm), low dark current (below 5 V), large bandwidth (12.4 GHz at 8.2 V), and low breakdown voltage (~7.8 V). The demonstrated device performance as well as the simple structure and good process compatibility can be attractive in future photo-detecting and advanced sensing applications.

Direct mapping and characterization of the surface local field in InGaAs/InP avalanche photodetectors

In this paper, InGaAs/InP avalanche photodetectors with a variety of guard ring structures are investigated. The electric distribution in the device is characterized by experiment and simulation methods to better understand the dark current mechanisms. It is found that deeper guard rings are more effective in preventing edge breakdown for the depressed lateral electric field. Scanning photocurrent microscopy measurement is used to characterize the effect of guard ring on InP layer. Our results show that deep guard ring design can reduce the surface electric field. In addition, the 1550 nm response distribution of optimized photodetectors under different operating modes is measured and compared. It shows guard ring can inhibit the edge breakdown. This work demonstrates the significance of guard ring designs of InGaAs/InP avalanche photodetectors, and the characterization method will provide an effective way to understand the source of the current generation mechanism.

Quantitative analysis of edge breakdown effect of Geiger mode avalanche photo-diodes utilizing optical probe scanning method

Planar InGaAs/InP avalanche photo diodes (APDs) are preferred single-photon detectors in the near-infrared region. They are usually fabricated using the double-diffusion method to avoid edge breakdown. However, this effect cannot be avoided completely as the bias voltage increases in the Geiger mode (GM). In this study, the influence of the deep diffusion window diameter on the premature edge breakdown of GM APDs was quantitatively analyzed using optical probe scanning method. Both numerical simulations and experimental measurements were performed. The electric field and dark current distribution, and the photon current under different optical input positions were numerically simulated. APDs with different deep diffusion window diameters were fabricated and tested to measure the photon current response. According to the normalized scanning photo current, we find that premature edge breakdown diminishes as the diffusion diameter of the device decreases. The position of the maximum electric field gradually shifted to the center as the diameter of the device decreased, and this shift gradually increased as the diameter decreased. The influence of edge breakdown was found to be avoided on the APD with a diameter of 10 μm, indicated by the avalanche gain reaching the maximum at the center, and the overlapping of optical and maximum electric gain regions is realized, which is crucial for high detection efficiency and low dark count of single photon detection.

Avalanche Photodiodes With Composite Charge-Layers for Low Dark Current, High-Speed, and High-Power Performance

In this work, a novel In_0.52Al_0.48As based top-illuminated avalanche photodiode (APD) is demonstrated. By combining the composite charge-layer design with a special p-side up etched mesa structure to zero the electric (E)-field at the periphery of this APD&#x0027;s multiplication (M-) layer, the edge breakdown phenomenon can be eliminated. This in turn leads to the simultaneous high-speed, high-saturation-power, high responsivity, and low-dark current performance characteristics of our APDs, which are essential for high-performance coherent receiver applications. The demonstrated device, with its simple top-illuminated structure exhibits a wide optical-to-electrical (O-E) bandwidth (21 GHz), high responsivity (5.5 A&#x002F;W at 0.9 V_br), and saturation current as high as 8 mA with a large active diameter of 24 &#x03BC;m for easy optical alignment. Furthermore, the nonlinear driving of a wavelength sweeping laser in the self-heterodyne beating setup can generate an optical pulse train like waveform, providing an effective optical modulation depth of up to 158&#x0025;, which leads to a maximum photo-generated RF power (at 10 GHz) from our APD as high as &#x002B;5.5 dBm. The excellent performance of our demonstrated APDs opens up new possibilities for the next generation of coherent receivers.

Extreme structure and spontaneous lift of spin degeneracy in doped perforated bilayer graphenes

Extreme structure and spin states of doped and undoped perforated bigraphenes was studied using DFT simulations. It was found that folded nanopores possess extremely high curvature of 0.34 Å−1. Dramatic structural deformation causes severe changes of the chemical properties of carbon atoms localized at the nanopores converting the folded edges to local oxidative fragments. It was found that asymmetrical coordination of either Li, Ca, or Al to the nanopores is coupled with electron transfer from metal to edge carbon atoms and breakdown of local inversion symmetry. Li-, Ca-, and Al-doped perforated AA bigraphene revealed ferromagnetic spin ordering with magnetic moments of 0.38, 0.14, and 0.32μB/unit cell, respectively, and spin polarization energy gain of 0.037eV for Ca-doped superlattice. It was shown that ferromagnetic spin ordering of bigraphene nanopores contradicts to the Nagaoka's theorem, which excludes strong electron correlations as a reason of spin polarization. Spontaneous lift of spin degeneracy was interpreted in terms of perturbing intense local electrostatic fields from extra electron charges localized at the nanopore edges, coupled with breakdown of space inversion and local translation invariances. It was shown that spin energy splitting is proportional to the matrix elements calculated on Bloch states with opposite wavevectors and perturbing electrostatic fields.

Modeling and Simulation of PGSPAD-Based Silicon Photomultipliers

This article presents and develops a novel comprehensive simulation model for perimeter gated single-photon avalanche diode-based silicon photomultipliers (PGSPAD SiPMs). A PGSPAD is a modification of single-photon avalanche diodes (SPADs) that contains a third terminal to mitigate perimeter edge breakdown. It does this without excessively enlarging the device area. The applied gate voltage modulates the dynamic range, breakdown voltage, and dark current characteristics. The proposed PGSPAD SiPM model correctly mimics the current–voltage transfer function and the avalanche-quench process of the SiPM detector and is verified by the experimental measurements of a PGSPAD SiPM fabricated in a commercial 0.5- $\mu \text{m}$ CMOS process. The model includes the dark current of the PGSPAD device. This was not included in previous SiPM models. The effect of the number of triggered microcells versus the total number of microcells and the impact of different parameters on the PGSPAD SiPM performance with added gate terminal are evaluated. The photon–electron spectrum with the effect of an extra gate terminal has been studied. Simulation results show very good agreement with experimental measurements.

Porous PTFE reinforced SPEEK proton exchange membranes for enhanced mechanical, dimensional, and electrochemical stability

The pores of polytetrafluoroethylene (PTFE) film were filled with the sulfonated poly (ether ketone) (SPEEK) electrolyte molecules to prepare the proton exchange membrane with the enhanced mechanical, dimensional and electrochemical stability for fuel cell application. Catechol/polyethyleneimine was co-deposited on the PTFE pore surface as an adhesive mediator for the feasible impregnation of SPEEK. The chemical composition, morphology, and wettability of the porous PTFE film were investigated by electron spectroscopy for chemical analysis, scanning electron microscope, mercury porosimetry, and water contact angle measurements. After pore filling with SPEEK electrolytes, several essential properties of membranes (e.g. water uptake, proton conductivity, mechanical property) and wet/dry cyclic cell performance were examined. The prepared pore-filled electrolyte membranes showed the superior mechanical and dimensional stability at the reduced water uptake to the pristine SPEEK membrane. Those excellent properties of the electrolyte membranes are reflected in the stable electrochemical cell performance over the repeated wet/dry cycles with suppression of crack/void formation and edge breakdown.

High-Power and High-Responsivity Avalanche Photodiodes for Self-Heterodyne FMCW Lidar System Applications

In this work, we demonstrate the high-power and high-responsivity performance of the dual multiplication (M-) layers in In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.48</sub> As based avalanche photodiode (APD). The dual M-layer design in our APD structure effectively constrains the multiplication process to a thin high-field region rather than the whole thick M-layer. It thus minimizes the space charge effect (SCE) within and avoids increasing the tunneling dark current for the case of directly shrinking M-layer thickness in APD. Furthermore, by combining the specially designed mesa shape with this dual M-layer structure, the edge breakdown can be well suppressed. These benefits lead to an ultra-high gain-bandwidth product (450 GHz; 1 A/W at unit gain) and a high saturation current (>12 mA) can be simultaneously achieved in our device. By nonlinearly driving a wavelength sweeping laser in the self-heterodyne lidar setup, it can generate an optical pulse train-like waveform, providing an effective optical modulation depth of 200% to feed into our demonstrated APD at the receiver-end. Under such scheme, the photo-generated RF (1 GHz) power from our APD with a 6.3 A/W responsivity can be as high as +6.95 dBm at a high (7 mA) output photocurrent. Such high-power and high-responsivity characteristics of our APD can further improve the signal-to-noise (S/N) ratio and dynamic range performances in each pixel of the lidar image. A high-quality 3-dimensional (D) FMCW lidar image is constructed based on our APD, without the integration of any electrical amplifier at the receiver end.

A Digital CMOS Silicon Photomultiplier Using Perimeter Gated Single Photon Avalanche Diodes With Asynchronous AER Readout

This paper presents a new architecture for a perimeter gated single photon avalanche diodes (PGSPADs) based CMOS digital silicon photomultiplier (SiPM) with fully digital asynchronous address event representation (AER) readout. A PGSPAD is a single photon avalanche diode with an additional polysilicon gate and mitigates the perimeter edge breakdown, modulates the noise floor, dynamic range, and sensitivity of the device. Spatial and temporal data compression techniques in the SiPM pixel improve dead time, and reduce electronics. Fill factor is improved using a compact, low power analog counter. The dead time improves by 25% with temporal compression improving by a factor of 10 for the pixel microcell. A $4\times 4$ pixel array in a standard $0.5~\mu \text{m}$ CMOS process is fully characterized for the dark counts as function of gate and excess bias as well as varying optical intensity. The array-level dynamic range is 142 dB.