Avalanche Triggering Research Articles

An accurate circuit model of Ge/Si single photon avalanche diode

Ge/Si single-photon avalanche diodes (SPADs) have benefits of low after-pulsing probability, low-cost and compatibility with CMOS electronics compared to InGaAs/InP counterpart, thus presenting great potentials for imaging and optical quantum applications in short-wave infrared (SWIR). In this work, an equivalent circuit model mimicking the behavior of pseudo-planar Ge/Si SPAD is constructed to provide accurate electronic information for the co-design of front-end circuit. The DC properties are modelled by nonlinear resistors, voltage-controlled switches and voltage sources, and the AC characteristics are emulated by junction and stray capacitances. To accurately evaluate the statistical behavior, thermal excitation and trap-assisted tunneling are incorporated in the built SPAD circuit models, where three-level traps are adopted to effectively fit the after-pulsing probability. The key model parameters such as electric field profile, breakdown voltage and avalanche triggering probability, are extracted from 2D device simulation. The developed Ge/Si SPAD circuit model implemented in Verilog-A hardware description language (HDL) with a gated passive quenching/reset architecture is validated by circuit simulation platform. The simulation results are in good agreement with the previously reported measurement data, demonstrating the effectiveness and accuracy of our Ge/Si SPAD circuit model.

A Study on Avalanche-Triggering Factors and Activity Characteristics in Aerxiangou, West Tianshan Mountains, China

Through analyzing the triggering factors and activity characteristics of avalanches in Aerxiangou in the Western Tianshan Mountains, the formation and disaster-causing process of avalanches were studied to provide theoretical support and a scientific basis for avalanche disaster prevention. In this paper, based on remote sensing interpretation and field investigation, a spatial distribution map of avalanches was established, and the induced and triggering factors in disaster-prone environments were analyzed using the certainty factor model. The degree of influence (E) of the disaster-causing factors on avalanche triggering was quantified, and the main control conditions conducive to avalanche occurrence in different periods were obtained. The RAMMS-avalanche model was used to analyze the activity characteristics at points where multiple avalanches occurred. Research results: (1) The E values of the average temperature, average snowfall, and surface roughness in February were significantly higher than those of other hazard-causing factors, reaching 1.83 and 1.71, respectively, indicating strong control. The E values of the surface cutting degree, average temperature, and average snow depth in March were all higher than 1.8, indicating that these control factors were more prominent than the other factors. In contrast, there were four hazard-causing factors with E values higher than 1.5 in April: the mean temperature, slope, surface roughness, and mean wind speed, with clear control. (2) Under the influence of the different hazard-causing factors, the types of avalanches from February–April mainly included new full-layer avalanches, surface avalanches, and full-layer wet avalanches. (3) In the RAMMS-avalanche simulation test, considering the deposition effect, compared to the previous avalanche movement path, the secondary avalanche flow accumulation area impact range changes were slight, while the movement area within the avalanche path changes was large, as were the different categories of avalanches and their different movement characteristic values. Overall, wet snow avalanches are more hazardous, and the impact force is larger. The new snow avalanches start in a short period, the sliding rate is fast, and the avalanche sliding surface (full-snow surface and face-snow) of the difference is mainly manifested in the differences in the value of the flow height.

Advanced Back-Illuminated Silicon Photomultipliers With Surrounding P+ Trench

This study conducted the TCAD simulation of an advanced back-illuminated silicon photomultipliers (BI-SiPM) device. This BI-SiPM structure with pixels was surrounded by a p+ trench, which conducted the p+ implant region available on the surface toward the back side. The removal of the metal layer from the incident SiPM surface reduced the blocking of incident light and improved the fill factor of single pixels. Therefore, the photon detection efficiency of BI-SiPM was improved to approximately 70% when the bias voltage was 5 V. The TCAD device simulations were performed to study this BI-SiPM structure, and the quenching process based on Mixedmode emulator was investigated to introduce the BI-SiPM pixel structure into a SPICE circuit. The results indicated that the proposed design could improve the uniform distribution of the electric field and avalanche triggering probability on a photon illuminating surface and increase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FF</i> , without affecting the crosstalk between pixels. Moreover, the design consideration of manufacturing process flow for BI-SiPM was proposed.

The lock-on effect and collapsing bipolar Gunn domains in high-voltage GaAs avalanche p-n junction diode

We present experimental evidence and physics-based simulations of the lock-on effect in high-voltage GaAs avalanche diodes. The avalanche triggering is initiated by steep voltage ramp applied to the diode and in-series 50 Ω load. After subnanosecond avalanche switching the reversely biased GaAs diode remains in the conducting state for the whole duration of the applied pulse (dozens of nanoseconds). There is no indication of the p-n junction recovery that is commonly expected to develop on the nanosecond scale due to the drift extraction of non-equilibrium carriers. The diode voltage keeps a constant value of ∼70 V much lower than the stationary breakdown voltage of 400 V. Numerical simulations reveal that the conducting state is supported by impact ionization in narrow high-field collapsing Gunn domains as well as in quasi-stationary cathode and anode ionizing domains. Collapsing Gunn domains spontaneously appear in the dense electron-hole plasma due to the negative differential mobility of electrons in GaAs. The effect resembles the lock-on effect of GaAs bulk photoconductive switches but is observed in reversely biased p-n junction diode switched by a non-optical method.

АКТИВНЫЕ ВОЗДЕЙСТВИЯ НА СНЕЖНЫЕ ЛАВИНЫ. РЕЗУЛЬТАТЫ ИССЛЕДОВАНИЙ И ОПЕРАТИВНО-ПРОИЗВОДСТВЕННЫХ РАБОТ

The results of long-term studies on the problems of forecasting avalanche risk and active avalanche control carried out in various organizations on the territory of the former USSR are presented. The studies were performed at specially equipped high-mountain avalanche stations, which made it possible to obtain experimental data on the snow cover mechanics and the dynamic parameters of avalanches. The results allowed developing a technology for preventive avalanche triggering based on the prediction of avalanche risk, the diagnosis of snow in the avalanche area, and the dynamic impact on snow stability. In most situations, the prevention of avalanches dangerous to humans and vital activity facilities includes a set of special avalanche safety measures based on active and passive avalanche defense.

Bit Error Performance of APD and SPAD Receivers in Optical Wireless Communication

This review concentrates on the state-of-the-art hardware-oriented receiver aspects for optical wireless communication (OWC), and points to the importance of BER performance analysis and modeling in presence of non-perpendicular light incidence. Receivers in OWC networks for 6G applications have to work for strongly different light incidence angles, to allow the formation of connections to locally separated transceivers without the need for rotation units and accurate adjustment. In turn, and in combination with fully integrated optical receivers, reduction of cost and increased comfort can be achieved. Fully integrated [bipolar] complementary metal-oxide-semiconductor ([Bi]CMOS) receivers with on-chip avalanche photodiodes (APDs) and single-photon avalanche diodes (SPADs) are presented and their performance in optical wireless communication is summarized. Impressive data rates up to 2 Gbit/s and free-space transmission distances up to 27 m at bit error ratios (BER) below 10−9 are reached with linear-mode APD receivers. The importance of optical interference in the isolation and passivation stack on top of the integrated photodiodes is illuminated. To be able to predict the dependence of the BER of single-photon avalanche diode (SPAD) receivers on the light incidence angle, a model, which includes a model for the photon detection probability and a standing-wave model for the isolation and passivation stack, is extended. The dependence of the BER on the light incidence angle onto the photodiodes is investigated by electromagnetic simulation for optical transmission of the layers on top of the photodiode, device simulation for the avalanche triggering probability and BER modeling with MATLAB. It is found that incidence angles up to 30° have moderate influence on the BER and that the BER degrades significantly for incidence angles larger than 50°.

Reconstructing the Snow Avalanche of Coll de Pal 2018 (SE Pyrenees)

Developments in mountain areas prone to natural hazards produce undesired impacts and damages. Thus, disaster assessment is mandatory to understand the physics of dangerous events and to make decisions to prevent hazardous situations. This work focusses on the practical implementation of methods and tools to assess a snow avalanche that affected a road at the Coll de Pal in 2018 (SE Pyrenees). This is a quite common situation in mountain roads and the assessment has to focus specially in the avalanche–road interaction, on the return periods considered and on the dynamics of the phenomena. This assessment presents the field recognition, snow and weather characterization and numerical modelling of the avalanche. Field campaigns revealed evidences of the avalanche triggering, runout trajectory and general behavior. An unstable situation of the snowpack due to a relatively large snowfall fallen some days before over a previous snowpack with weak layers, caused the avalanche triggering when an additional load was added by a strong wind-drift episode. A medium size (&lt;2500 m3) soft slab avalanche, corresponding to a return period of 15–20 years, occurred and crossed the road of the Coll de Pal pass. The event was reproduced numerically by means of the 2D-SWE based numerical tool Iber aiming to analyze the avalanche behavior. Results of the simulation corresponded with the observations (runout trajectory and snow deposit); thus, relevant information about the avalanche dynamics could be obtained. Identified differences probably come from the terrain elevation data, which represent “snow free” topography and do not consider the snowpack on the terrain.

An analytical solution for McIntyre’s model of avalanche triggering probability for SPAD compact modeling and performance exploration

Single photon avalanche diodes (SPADs) are widely used to monitor fast and weak optical signals. The modeling of two main figures of merit of SPAD, namely the dark count rate (DCR) and the photon detection probability, requires one to calculate the avalanche triggering probability (ATP), usually obtained by numerically solving two transcendental equations (the McIntyre model) as post processing of technology computer-aided design simulations. This paper proposes an analytical alternative to this approach, exploiting an approximation of the impact ionization rates, in principle valid only under high field conditions, but extended to all fields by a simple fitting procedure. The proposed approximated/analytical ATP calculation can be efficient and relevant for SPAD compact modeling that is compatible with a spice-like simulator. As an illustration, a full analytical calculation for DCR based on both ATP and generation terms for a P+N abrupt diode junction is presented.

Simulation of High-Efficiency Resonant-Cavity-Enhanced GeSn Single-Photon Avalanche Photodiodes for Sensing and Optical Quantum Applications

Two novel resonant-cavity-enhanced (RCE) GeSn single-photon avalanche photodiode (SPAD) detectors are designed and simulated for high-efficiency single-photon detection at 1550 and 2000 nm wavelength at room temperature for sensing and optical quantum applications. The RCE GeSn SPAD consists of a PIPIN GeSn/Si heterostructures embedded in an optical cavity formed by a distributed Bragg reflector (DBR) and GeSn surface. The results show that high photon absorption efficiency and avalanche triggering probabilities can be achieved by careful design of DBR reflectors, GeSn absorber, doping concentrations of Si charge sheet layer and multiplication layer, which lead to a high single-photon detection efficiency (SPDE) of ~80%, which is promising for emerging quantum applications demanding high SPDE, such as linear optical quantum computing. The noise equivalent power (NEP) and dark count rate (DCR) as a function of threading dislocations density (TDD) are examined as well. It is found that the device could operate near room temperature with a similar DCR level to that of Ge SPAD operating at low temperature. A NEP of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 3\times 10^{-15}$ </tex-math></inline-formula> W/Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{1/2}$ </tex-math></inline-formula> is observed from RCE GeSn SPAD for 1550 nm wavelength at room temperature. This work shows that the proposed RCE GeSn SPADs are promising candidates for high-efficiency single-photon detection in short-wave infrared (SWIR) regime for sensing and optical quantum applications.

Snow cornice and snow avalanche monitoring using automatic time lapse cameras in Tasiapik Valley, Nunavik (Québec) during the winter of 2017–2018

A series of automatic time-lapse cameras installed along the southwestern side of Tasiapik Valley, near the village of Umiujaq, Nunavik (northern Québec) documented several departure modes and types of snow involved in snow avalanches during winter 2017–2018. These included cornice–avalanche dynamics, slab and loose snow avalanches, and clean and dirty snow avalanches. At the top of the selected slope, a camera monitored the development of a snow cornice beginning in November 2017, detecting multiple cornice failures over the winter and spring. The track and deposition area of the runout paths were monitored from two cameras downslope, revealing the concomitance of snow–cornice fall and snow avalanche triggering. Snow avalanche activity remained relatively infrequent until the end of May 2018. Spring snow avalanche activity is characterized by wet and dirty snow avalanches carrying debris to the foot of the slope and by runout zones located near the road along the slope.

Optical and Electrical Characterization and Modeling of Photon Detection Probability in CMOS Single-Photon Avalanche Diodes

Single-photon avalanche diodes (SPADs) are very attractive devices in optical detector applications where both CMOS integration and low light detection are critical. An important SPAD performance parameter is the photon detection probability (PDP) which has to be carefully characterized for the sensor design. In this article, we present a comprehensive modeling and experimental characterization of the PDP to obtain its optical and electrical dependency on different parameters including the wavelength and light incidence angle as well as the biasing condition. By calculating the optical absorption and the avalanche triggering probabilities within the silicon, the PDP of an n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /p-well CMOS-implemented SPAD is accurately modeled. It is shown that due to the formation of a standing wave in different layers above the silicon, which significantly affects the optical transmission and the PDP spectrum, the application of the presented approach is necessary especially when an anti-reflection coating layer is not available. The obtained result shows an excellent agreement to our measurements and, therefore, the model can be reliably used for accurate design and optimization of SPAD-based detectors and to avoid very time-consuming experimental investigations, e. g. for obtaining the detector performance for deviations in the light incidence angle.

Ice: the paradigm of wild plasticity.

Ice plasticity has been thoroughly studied, owing to its importance in glaciers and ice sheets dynamics. In particular, its anisotropy (easy basal slip) has been suspected for a long time, then fully characterized 40 years ago. More recently emerged the interest of ice as a model material to study some fundamental aspects of crystalline plasticity. An example is the nature of plastic fluctuations and collective dislocation dynamics. Twenty years ago, acoustic emission measurements performed during the deformation of ice single crystals revealed that plastic 'flow' proceeds through intermittent dislocation avalanches, power law distributed in size and energy. This means that most of ice plasticity takes place through few, very large avalanches, thus qualifying associated plastic fluctuations as 'wild'. This launched an intense research activity on plastic intermittency in the Material Science community. The interest of ice in this debate is reviewed, from a comparison with other crystalline materials. In this context, ice appears as an extreme case of plastic intermittency, characterized by scale-free fluctuations, complex space and time correlations as well as avalanche triggering. In other words, ice can be considered as the paradigm of wild plasticity. This article is part of the theme issue 'The physics and chemistry of ice: scaffolding across scales, from the viability of life to the formation of planets'.

Characterization of SiPM Avalanche Triggering Probabilities

Silicon Photo-Multipliers (SiPMs) are detectors sensitive to single photons that are used to detect scintillation and Cherenkov light in a variety of physics and medical-imaging applications. SiPMs measure single photons by amplifying the photo-generated carriers (electrons or holes) via a Geiger-mode avalanche. The Photon Detection Efficiency (PDE) is the combined probability that a photon is absorbed in the active volume of the device with a subsequently triggered avalanche. Absorption and avalanche triggering probabilities are correlated since the latter probability depends on where the photon is absorbed. In this paper, we introduce a physics motivated parameterization of the avalanche triggering probability that describes the PDE of a SiPM as a function of its reverse bias voltage, at different wavelengths. This parameterization is based on the fact that in p-on-n SiPMs the induced avalanches are electron-driven in the ultra-violet and near-ultra-violet ranges, while they become increasingly hole-driven towards the near-infra-red range. The model has been successfully applied to characterize two Hamamatsu MPPCs and one FBK SiPM, and it can be extended to other SiPMs. Furthermore, this model provides key insight on the electric field structure within SiPMs, which can explain the limitation of existing devices and be used to optimize the performance of future SiPMs.

Modeling of Timing Jitter for Single Photon Avalanche Diodes

Timing jitter is an important indication reflecting on the performance of single photon avalanche diodes (SPADs). In this paper, an analytical model is established to predict the temporal response characteristic of SPADs based on the physical progress of photon absorbing and avalanche triggering. The diffusion and drift of carriers in the neutral layer are considered by solving the continuity equation for exponential tail modeling. A Gaussian distribution is used to model the peak response corresponding to photon absorption in avalanche region. The model key physic parameters such as electric field and avalanche triggering probability come from TCAD simulation, which improves the model accuracy. This analytical model is useful to predict the temporal response for given SPAD device structure.

An accurate behavioral model for single-photon avalanche diode statistical performance simulation

An accurate behavioral model is presented to simulate important statistical performance of single-photon avalanche diodes (SPADs), such as dark count and after-pulsing noise. The derived simulation model takes into account all important generation mechanisms of the two kinds of noise. For the first time, thermal agitation, trap-assisted tunneling and band-to-band tunneling mechanisms are simultaneously incorporated in the simulation model to evaluate dark count behavior of SPADs fabricated in deep sub-micron CMOS technology. Meanwhile, a complete carrier trapping and de-trapping process is considered in afterpulsing model and a simple analytical expression is derived to estimate after-pulsing probability. In particular, the key model parameters of avalanche triggering probability and electric field dependence of excess bias voltage are extracted from Geiger-mode TCAD simulation and this behavioral simulation model doesn't include any empirical parameters. The developed SPAD model is implemented in Verilog-A behavioral hardware description language and successfully operated on commercial Cadence Spectre simulator, showing good universality and compatibility. The model simulation results are in a good accordance with the test data, validating high simulation accuracy.

Comprehensive understanding of dark count mechanisms of single-photon avalanche diodes fabricated in deep sub-micron CMOS technologies

The dark count noise mechanisms of single-photon avalanche diodes (SPADs) fabricated in deep sub-micron (DSM) CMOS technologies are investigated in depth. An electric field dependence of tunneling model combined with carrier thermal generation is established for dark count rate (DCR) prediction. Applying the crucial parameters provided by Geiger mode TCAD simulation such as avalanche triggering probability and electric field distribution in the SPAD avalanche region, the individual contribution of each noise source to DCR is calculated for several SPADs in DSM CMOS technologies. The model calculation results reveal that the trap-assisted tunneling is the main DCR generation source for these DSM CMOS SPADs. With the increase of doping levels in the device avalanche region, the band-to-band tunneling will be the dominant factor that could lead to the higher DCR in scaled DSM CMOS technologies.

Simulation study of a novel 3D SPAD pixel in an advanced FD-SOI technology

In this paper, a novel SPAD architecture implemented in a Fully-Depleted Silicon-On-Insulator (SOI) CMOS technology is presented. Thanks to its intrinsic vertical 3D structure, the proposed solution is expected to allow further scaling of the pixel size while ensuring high fill factors. Moreover the pixel and the detector electronics can benefit of the well-known advantages brought by SOI technology with respect to bulk CMOS, such as higher speed and lower power consumption. TCAD simulations based on realistic process parameters and dedicated post-processing analysis are carried out in order to optimize and validate the avalanche diode architecture for an optimal electric field distribution in the device but also to extract the main parameters of the SPAD, such as the breakdown voltage, the avalanche triggering probability, the dark count rate and the photon detection probability. A comparison between the efficiency in back-side and front-side approaches is carried out with a particular focus on time-of-flight applications.

A new modeling and simulation method for important statistical performance prediction of single photon avalanche diode detectors

This paper presents a new modeling and simulation method to predict the important statistical performance of single photon avalanche diode (SPAD) detectors, including photon detection efficiency (PDE), dark count rate (DCR) and afterpulsing probability (AP). Three local electric field models are derived for the PDE, DCR and AP calculations, which show analytical dependence of key parameters such as avalanche triggering probability, impact ionization rate and electric field distributions that can be directly obtained from Geiger mode Technology Computer Aided Design (TCAD) simulation. The model calculation results are proven to be in good agreement with the reported experimental data in the open literature, suggesting that the proposed modeling and simulation method is very suitable for the prediction of SPAD statistical performance.

Dendrogeomorphic reconstruction of snow avalanche regime and triggering weather conditions

While dendrogeomorphology has been recognized as a useful tool to identify past avalanche activity, there is only a handful of papers that focus on the assessment of weather or climatic triggers of tree-ring reconstructed avalanche events. This paper compares the potential of logistic regression and classification tree algorithms to highlight weather scenarios responsible for the occurrence of high-magnitude avalanche activity in the Presidential Range of the White Mountains, New Hampshire (USA). Our tree-ring procedure improves the modern GD- It threshold with the implementation of a second criteria based on the Moran index. 450 trees sampled in seven different avalanche paths allowed us to reconstruct 45 avalanches that occurred during 19 different years for the period 1936–2012. The results show that while statistically significant, the logistic regression models are less accurate than classification trees to assess avalanche activity based on annual and monthly weather variables. Moreover, even if snow related covariates are located at the root node of every classification tree model, the addition of temperature and wind predictors increases their robustness. This suggests that high-magnitude avalanches in the Presidential Range not only respond to snow, but also to atmospheric conditions responsible for the creation of weak layers within the snowpack.

Mapping starting zone snow depth with a ground-based lidar to assist avalanche control and forecasting

The distribution of snow depth in avalanche starting zones exerts a strong influence on avalanche potential and character. Extreme depth changes over short distances are common, especially in wind-affected, above-treeline environments. Snow depth also affects the ease of avalanche triggering. Experience shows that avalanche reduction efforts are often more successful when targeting shallow trigger point areas near deeper slabs with explosives or ski cutting. Our paper explores the use of high-resolution (cm scale) snow depth and snow depth change maps from terrestrial laser scanning (TLS) data to quantify loading patterns for use in both pre-control planning and in post-control assessment.We present results from a pilot study in three study areas at the Arapahoe Basin ski area in Colorado, USA. A snow-free reference data set was collected in a summer TLS survey. Mapping multiple times during the snow season allowed us to produce time series maps of snow depth and snow depth change at high resolution to explore depth and slab thickness variations due to wind redistribution. We conducted surveys before and after loading events and control work, allowing the exploration of loading patterns, slab thickness, shot and ski cut locations, bed surfaces, entrainment, and avalanche characteristics. We also evaluate the state of TLS for use in operational avalanche control settings.