Avalanche Current Research Articles

Compact Active Quenching Circuit for Single Photon Avalanche Diodes Arrays

A compact quenching circuit for Single Photon Avalanche Diode (SPAD) arrays is presented. The proposed circuit preserves the advantages of small area occupation and low power consumption, since it mainly adopts the junction capacitance of the detector to sense the avalanche current. The sensing time is now limited more by the detector rather than the circuit itself. Fabricated in TSMC standard 0.35[Formula: see text][Formula: see text]m CMOS process, the proposed circuit only occupies an area of 20[Formula: see text][Formula: see text]m[Formula: see text][Formula: see text][Formula: see text]31[Formula: see text][Formula: see text]m and can operate properly with the detector biased up to 5[Formula: see text]V above breakdown. The circuit functionality has been verified by experimental measurements, operating with 64[Formula: see text][Formula: see text][Formula: see text]64 InGaAs/InP single photon avalanche diode arrays for time-of-flight-based applications.

The Effect of Electrothermal Nonuniformities on Parallel Connected SiC Power Devices Under Unclamped and Clamped Inductive Switching

Nonuniformities in the electrothermal characteristics of parallel connected devices reduce overall reliability since power is not equally dissipated between the devices. Furthermore, a nonuniform rate of operational degradation induces electrothermal variations thereby accelerating the development of failure. This paper uses simulations and experiments to quantitatively and qualitatively investigate the impact of electrothermal variations on the reliability of parallel connected power devices under unclamped inductive switching (UIS) conditions. This is especially pertinent to SiC where small die areas mean devices are often connected in parallel for higher current capability. Measurements and simulations show that increasing the variation in the initial junction temperatures and switching rates between parallel connected devices under UIS reduces the total sustainable avalanche current by 10%. It is seen that the device with the lower junction temperature and lower switching rate fails. The measurements also show that the maximum sustainable avalanche energy for a given variation in junction temperature and switching rate increases with the avalanche duration, meaning that the effect of electrothermal variation is more critical with high power (high current and low inductor) UIS pulses compared with high energy (low current and high inductance) pulses. These results are important for condition monitoring and reliability analysis.

Evaluation of SiC MOSFET power modules under unclamped inductive switching test environment

High power commercial SiC MOSFET modules have been evaluated under unclamped inductive switching (UIS) environment from the point of view of judging their failure ruggedness. The power modules with 1.7kV/300A and 1.2kV/180A rating were stressed with avalanche currents of their rated current value. One SiC MOSFET module sustained its avalanche current value when tested at rated forward current condition (i.e., 180A) while the other power module failed during avalanche test even before reaching to its nominal rating current value (i.e., 300A) at 25°C. It is further shown that avalanche current of SiC-MOSFET modules is approximately insensitive of temperature variation under UIS behavior. A maximum avalanche energy of 2.43 and 3.23J was extracted when tested at maximum avalanche current of 165 and 220A for 1.7kV/300A and 1.2kV/180A rated power modules, respectively. These numbers far exceed than that of equivalent Si based IGBTs.

What does it take to detect entanglement with the human eye?

Tremendous progress has been realized in quantum optics for engineering and detecting the quantum properties of light. Today, photon pairs are routinely created in entangled states. Entanglement is revealed using single-photon detectors in which a single photon triggers an avalanche current. The resulting signal is then processed and stored in a computer. Here, we propose an approach to get rid of all the electronic devices between the photons and the experimentalist, i.e., to use the experimentalist’s eye to detect entanglement. We show in particular that the micro-entanglement that is produced by sending a single photon into a beam splitter can be detected with the eye using the magnifying glass of a displacement in phase space. The feasibility study convincingly demonstrates the possibility of realizing the first experiment where entanglement is observed with the eye.

Interview

Dr Niksa Tadic from the University of Montenegro talks to us about the work behind the paper ‘A 100 MHz current generator with T/(T-t) time waveform in 0.35 μm BiCMOS technology model’, page 744. Dr Niksa Tadic In 1995, after three years of industrial experience, I joined the University of Montenegro, Faculty of Electrical Engineering. I am interested in optoelectronic integrated circuit design including optical receivers with variable transimpedances, red-green-blue optical sensors, and current drivers for laser diodes in both CMOS and BiCMOS technologies. At the moment, together with my colleagues from the EMCE Institute in Vienna and the University of Montenegro in Podgorica, I am working on negative resistance based voltage amplifiers. The small-signal amplification approach based on the shifting of a DC operating point along the linear part of the voltage amplifier's transfer characteristic has become questionable in deep submicron technologies. The slope of the linear part of the amplifier's transfer characteristic reduces with the decrease of transistors dimensions, causing decrease of the voltage gain. The nonlinear small-signal amplification method based on negative resistance could be used as an alternative to the linear approach. I have reported in Electronics Letters a design of a current generator suitable for optical quantum random number generation (OQRNG), designed in 0.35 mm BiCMOS technology, with T/(T-t) time dependence. Logarithmic converter and differentiator used in an existing design have been avoided in the proposed design by using the BJT translinear loop. The achieved frequency bandwidth of the current pulses of 100 MHz is 5 times larger in comparison to the state-of-the-art, with at least 20 times smaller power consumption. The relative error of the measured waveform at 20 MHz is less than 3% in 97.5% of the time interval in which the current pulses have a rising slope. A generator based on a random physical phenomenon is the only method to obtain true random numbers. OQRNG based on the randomness of detecting single photons is of special interest because of its fast generation of random numbers and reliability. Hence, the proposed current generator with T/(T-t) time dependence can be applied in all those fields where true random numbers are needed, such as cryptography, statistical analysis, numerical simulations, or lottery games. In addition to the mentioned negative resistance based voltage amplifiers, I am working on further improvement of the OQRNG based on the proposed current generator with T/(T-t) time dependence. During the last 12 years of my research in optoelectronics, among the other specific applications in the field, there have been efforts toward research and development of optical detectors of various types (especially photodiodes), optical receivers with variable transimpedances intended for the universal optical storage systems (CD, DVD, Blu-Ray), colour sensors, and optical distance measurement systems. In the future, without any doubt, one of the main research interests in the field of optoelectronics will be the systems for detection of weak optical signals based on single photon avalanche diodes (SPADs). When a single photon is absorbed in the space-charge region of the SPAD, an electron-hole pair is generated. Due to the high electric field, additional electron-hole pairs are generated causing the rapid rise of the avalanche current. The avalanche current must be quenched to allow the detection of the next photon. To provide data transfer based on weak optical signals in the GHz region, the quenching of the avalanche current should be performed very fast, typically within 1 ns. This task is a great challenge for researchers in this area.

Voltage sharing effect and interface state calculation of a wafer-bonding Ge/Si avalanche photodiode with an interfacial GeO2 insulator layer.

The tunneling effect and interface state in the p-Ge/GeO2p-Si structure of a wafer-bonding Ge/Si avalanche photodiode (APD) are investigated. It is found that the thin interfacial GeO2 layer (1-2 nm) formed by the hydrophilic reaction at the wafer-bonding interface significantly affects the performance of the Ge/Si APD. With the increase of the GeO2 thickness, the dark current of the Ge/Si APD decreases enormously due to the blocking effect of this GeO2 layer. Owing to the carrier accumulation in Ge layer under illumination condition, the voltage sharing effect of the GeO2 layer (thicker) becomes serious, leading to the absence of the electric field in Ge layer. The photon-generated electrons at Ge/GeO2 interface can be captured and released by the interface states at certain reverse bias. This can adjust the avalanche current of the Ge/Si APD. The stronger interface recombination induced by the larger interface state density (ISD) results in the decrease of the electric field in Ge layer. This increases the transit time of carriers, which in turn decreases the 3dB-bandwidth. Due to the drastic increase of the dark current (larger ISD), the gain of the Ge/Si APD decreases.

高誘電率絶縁膜を用いたフィールドプレート電極を有する縦型GaNダイオード

GaN high voltage diodes with high-k dielectrics passivation underneath the filed plate are demonstrated. Simulation results at reverse voltage of 1000V showed that the maximum electric field near the mesa-etched pn junction edges covered with film of dielectric constant k value of 10 was reduced to 2.3MV/cm from 3.2MV/cm (SiO2(k=3.9)). Mesa structures of pn junction diodes were fabricated by ICP dry etching, and mixed oxide of SiO2 & CeO2 dielectric film with k value of about 12.3 was deposited by CVD. I-V characteristics of the diode with a field plate showed the breakdown voltage above 2000 V with an increased avalanche current. This means that the electric field reduces at the periphery of the mesa etched pn junction and was uniformly formed across the whole pn junction. It is clear that high-k dielectric film passivation and filed plate termination are essential techniques for GaN power devices.

A 2-GHz Bandwidth, Integrated Transimpedance Amplifier for Single-Photon Timing Applications

In recent years, single-photon timing techniques have been employed in a steadily increasing number of applications. Most of these applications require high detector performance in terms of noise, photon detection efficiency, time resolution, and number of pixels operating in parallel. The detectors best fitting these requirements are single-photon avalanche diode (SPAD) arrays built in custom technology, although the systems based on such detectors are limited to a few pixels. In this paper, we present a novel read-out circuit, developed in a 0.18- $\mu $ m high voltage-CMOS technology, for the detection of the SPAD avalanche current: the designed circuit is based on a 2.2-GHz bandwidth integrated transimpedance amplifier, followed by a low-pass filter, to reduce crosstalk, and by an integrated comparator. The pick-up circuit has a total power dissipation of 1.1 mW, occupies an overall area of 15500 $\mu $ $\mathrm{m}^{2}$ and shows a time resolution down to 48 ps and a negligible crosstalk between two different pixels. All these features can open the way to the development of large SPAD arrays, characterized by a performance comparable with that of the single-pixel structures. Moreover, the good agreement between the simulated and the measured resolution (with a 14% maximum error) makes the future improvement of the evaluated performance possible.

Avalanche Capability of Vertical GaN p-n Junctions on Bulk GaN Substrates

Inductive avalanche test results presented in this letter demonstrate that GaN p-n diodes can sustain single-pulse and repetitive inductive avalanche currents. The 0.36-mm2 vertical GaN p-n diodes can sustain single-pulse avalanche currents as high as 10 A. The safe zone of the single-pulse avalanche current is limited by peak pulse power and energy deposited in the device. The temperature-dependent behavior of the breakdown voltage and the reverse-voltage at onset of avalanche has a positive temperature coefficient. Repetitive avalanche ruggedness testing was performed by applying $10^{\mathrm {5}}$ pulses at 5-kHz frequency with increasing repetitive stress current. Based on a population of 63 devices, the incremental failure rate under repetitive avalanche current increases with increasing avalanche current. The devices that survive the step stress test sustain no parametric drift under repetitive avalanche.

Compact CMOS active quenching/recharge circuit for SPAD arrays

SummaryAvalanche diodes operating in Geiger mode are able to detect single photon events. They can be employed to photon counting and time‐of‐flight estimation. In order to ensure proper operation of these devices, the avalanche current must be rapidly quenched, and, later on, the initial equilibrium must be restored. In this paper, we present an active quenching/recharge circuit specially designed to be integrated in the form of an array of single‐photon avalanche diode (SPAD) detectors. Active quenching and recharge provide benefits like an accurately controllable pulse width and afterpulsing reduction. In addition, this circuit yields one of the lowest reported area occupations and power consumptions. The quenching mechanism employed is based on a positive feedback loop that accelerates quenching right after sensing the avalanche current. We have employed a current starved inverter for the regulation of the hold‐off time, which is more compact than other reported controllable delay implementations. This circuit has been fabricated in a standard 0.18 µm complementary metal‐oxide‐semiconductor (CMOS) technology. The SPAD has a quasi‐circular shape of 12 µm diameter active area. The fill factor is about 11%. The measured time resolution of the detector is 187 ps. The photon‐detection efficiency (PDE) at 540 nm wavelength is about 5% at an excess voltage of 900 mV. The break‐down voltage is 10.3 V. A dark count rate of 19 kHz is measured at room temperature. Worst case post‐layout simulations show a 117 ps quenching and 280 ps restoring times. The dead time can be accurately tuned from 5 to 500 ns. The pulse‐width jitter is below 1.8 ns when dead time is set to 40 ns. Copyright © 2015 John Wiley & Sons, Ltd.

Improved Electrothermal Ruggedness in SiC MOSFETs Compared With Silicon IGBTs

A 1.2-kV/24-A SiC-MOSFET and a 1.2-kV/30-A Si-Insulated gate bipolar transistor (IGBT) have been electrothermally stressed in unclamped inductive switching conditions at different ambient temperatures ranging from −25 °C to 125 °C. The devices have been stressed with avalanche currents at their rated currents and 40% higher. The activation of the parasitic bipolar junction transistor (BJT) during avalanche mode conduction results from the increased body resistance causing a voltage drop between the source and body, greater than the emitter-base voltage of the parasitic BJT. Because the BJT current and temperature relate through a positive feedback mechanism, thermal runaway results in the destruction of the device. It is shown that the avalanche power sustained before the destruction of the device increases as the ambient temperature decreases. SiC MOSFETs are shown to be able to withstand avalanche currents equal to the rated forward current at 25 °C, whereas IGBTs cannot sustain the same electrothermal stress. SiC MOSFETs are also shown to be capable of withstanding avalanche currents 40% above the rated forward current though only at reduced temperatures. An electrothermal model has been developed to explain the temperature dependency of the BJT latchup, and the results are supported by finite-element models.

Evaluation of SiC Stack Cascode for 200°C Operations

This paper evaluates the static and dynamic characteristics of a 1.2kV SiC stack-cascode at junction temperatures (Tj) up to 200°C. The experimental results show that, at Tj = 200°C, the SiC stack-cascode can be switched stably under a 600V-17A inductive load condition and can withstand an avalanche current of 13A for 9μs (Eav = 116mJ) for a 1.5mH load inductor. The SiC stack-cascode has no degradation in on-resistance, threshold voltage and blocking characteristics after 80 hours HTRB reliability test at 200°C ambient. These promising experimental results indicate the possibility of the SiC stack-cascode for reliable 200°C operations.

Avalanche Current Waveform Estimated From Electroluminescence in InGaAs/InP SPADs

We demonstrated that the avalanche current waveform in InGaAs/InP single-photon avalanche diodes (SPADs) can be estimated from the measurement of the electroluminescence emitted by the SPAD itself. We simultaneously acquired and compared both optical and electrical waveforms and we extracted the dependence of avalanche current on electroluminescence, showing that the number of collected photons is almost proportional to the number of carriers flowing through the p-n junction, whereas the excess bias (that sets the electric field in the multiplication region when the avalanche is triggered) has a negligible impact. This non-invasive optical technique for estimating the avalanche current can be used when the electrical measurements of the SPAD current are not feasible.

Fast Active Quenching Circuit for Reducing Avalanche Charge and Afterpulsing in InGaAs/InP Single-Photon Avalanche Diode

We characterize three different quenching circuits for InGaAs/InP single-photon avalanche diodes (SPADs) operated in gated mode: i) a simple passive quenching circuit; ii) an active quenching circuit; and iii) a fast active quenching circuit. For each of these, we acquire the shape of the avalanche current, at different excess biases, by reconstructing the waveform of the photons emitted from the detector during an avalanche and we simultaneously measure the afterpulsing probability and the dependence of dark count rate on gate period (to estimate the maximum count rate). We prove that the avalanche charge reduction is in agreement with the reduction of afterpulsing probability, giving a four-time decrease in afterpulsing when employing the fast active quenching circuit compared to the simple passive quenching circuit.

High-Speed Photon-Number Resolving With Sinusoidally Gated Multipixel Photon Counters

We demonstrate a high-speed photon-number-resolving detector based on a sinusoidally gated multipixel photon counter (MPPC) at a repetition rate of 200 MHz. Two steps of low-pass filters are used to minimize the MPPC's capacitive response noise in sinusoidally gated Geiger mode, resulting in the efficient detection of weak photon-induced avalanche currents. Compared with passive quenching schemes, the sinusoidal gating scheme is conducive to shortening the recovery time for each pixel of the MPPC to detect the next coming photons, thus improving the detector's photon-number-resolving capability at a high repetition rate. The gated MPPC can identify the photon numbers of the incident pulses with a repetition frequency of 50 MHz clearly at as high as an average of 7.22 photons/pulse detected before saturation at room temperature.

Secondary effects on electron multiplication in pure isobutane

The presence of secondary processes in electron multiplication under high uniform electric fields at atmospheric pressure in pure isobutane was investigated. The experimental setup consists of a Resistive Plate Chamber-like cell with the anode made of a high resistivity glass (2×1012Ωcm) and a metallic cathode, on which photoelectrons are produced by the incidence of a pulsed laser beam. In particular, the dependence of the first Townsend coefficient (α) on the repetition rate and the intensity of the UV laser pulses was studied. The E/N range considered spanned from ≈145 to ≈200Td. The α coefficient was determined by measuring both the primary ionization and the avalanche currents with the help of an electrometer, directly connected to the cathode. Of all the investigated secondary effects, only the ohmic drop across the resistive glass has been found to be non-negligible in the present experimental conditions and has been corrected for. The obtained values are compared with Magboltz simulation results and presented in tabular form.

New perspective on passively quenched single photon avalanche diodes: effect of feedback on impact ionization

Single-photon avalanche diodes (SPADs) are primary devices in photon counting systems used in quantum cryptography, time resolved spectroscopy and photon counting optical communication. SPADs convert each photo-generated electron hole pair to a measurable current via an avalanche of impact ionizations. In this paper, a stochastically self-regulating avalanche model for passively quenched SPADs is presented. The model predicts, in qualitative agreement with experiments, three important phenomena that traditional models are unable to predict. These are: (1) an oscillatory behavior of the persistent avalanche current; (2) an exponential (memoryless) decay of the probability density function of the stochastic quenching time of the persistent avalanche current; and (3) a fast collapse of the avalanche current, under strong feedback conditions, preventing the development of a persistent avalanche current. The model specifically captures the effect of the load's feedback on the stochastic avalanche multiplication, an effect believed to be key in breaking today's counting rate barrier in the 1.55-μm detection window.

Electrical behavior research of silicon-on-insulator SiGe heterojunction bipolar transistor

The paper deals with the design optimization of SiGe heterojunction bipolar transistor (HBT) on thin film silicon-on-insulator (SOI). The basic DC and AC current characteristics are obtained and the differences between the SOI and bulk SiGe HBT are analyzed. As the incorporation of SOI substrate makes the SOI SiGe HBT a four-terminal device, the influences of the substrate bias on Gummel plot, output current and avalanche current are studied emphatically. Finally, the physical parameters of material and geometric parameters of the device are discussed by changing the frequency characteristics. Compared with the bulk counterpart, the SOI SiGe HBT is designed and fabricated with a great degree of freedom for better performance. This systematic analysis of SOI SiGe HBT provides a valuable reference for the SOI SiGe BiCMOS circuit design and simulation.

Electric field unbalance for robust floating ring termination

The electric field balancing in the guard-ring edge termination structure of 600V class Super-Junction devices is studied. The relation of the lateral electric field across the racetrack structure and the robustness of the structure against avalanche currents is investigated through experimental data and TCAD simulations. It has been found that the electrical field must be substantially imbalanced to achieve good ruggedness. The effect of the P-ring dose on the electrical performances of punch-through PiN diodes is also investigated.

Laboratory demonstration of runaway electron breakdown of air

Results of experiments demonstrating the phenomenon of runaway electron breakdown of atmospheric air under laboratory conditions are presented. As the discharge-initiating electron beam of duration ∼ 50 ps had passed through the electrode gap, a runaway electron avalanche current was detected in the electrode gap downstream of the anode grid and then breakdown occurred with picosecond stability. The maximum electron energy and the duration of the avalanche current corresponded to theoretical notions about the runaway electron breakdown of atmospheric air in a strong electric field. Breakdown did not occur at all or was considerably delayed when no initiating beam was used.