Avalanche Breakdown Phenomena Research Articles

High performance Au/mix-phase MgZnO/Ga-doped ZnO/In heterojunction solar-blind UV detector with small work voltage

High performance UVC (220 nm–280 nm) detectors with low work voltage is key problem in wide application of UVC optoelectronic device. Here, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is made with both high UVC sensitivity mix-phase MgZnO and high carrier density Ga-doped ZnO conductive layers. The heterostructure detector possess relative high response(0.36A/W)at 254 nm deep UV light without bias voltage. The avalanche breakdown phenomenon within the heterojunction detector, introduced high deep UV response (1390.3 A/W at 3.3 μW/cm2 230 nm) of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector under 5 V bias voltage. The high response of Au/MgZnO/Ga-doped ZnO/In heterojunction detector under low work voltage, is not only much higher than MSM structure MgZnO detector under bias voltage over 25 V, but also higher than reported deep UV detector under small bias voltage. In addition, because of different internal breakdown mechanism, the peak response position of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector is located at shorter wavelength position compared with MSM structure MgZnO detector. Therefore, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is an ideal device structure in low voltage driven detector with relative high response at short wavelength UV light.

Polyaniline Hybrids with Biological Tissue, and Biological Polymers as Physiological—Electroactive Materials

A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. Optical microscopy observation revealed that polyaniline was deposited into the micro-tissue of the sprout to form the conductive polymer bio-composite. Micro-optical fiber functions for the composite were visually confirmed. Furthermore, the sprout/polyaniline based organic diode exhibited an avalanche breakdown phenomenon. Next, a fucoidan/polyaniline composite as a physiological active material/conducting polymer composite was prepared. This composite showed good film-forming ability, electrochromism, and a micro-porous surface. This paper reports the preparation of conducting polymer composites with a combination of bio-tissue and bio-substance for the creation of bio-based electrically active organized architecture.

Ultrasensitive Photodetection in MoS2 Avalanche Phototransistors.

Recently, there have been numerous studies on utilizing surface treatments or photosensitizing layers to improve photodetectors based on 2D materials. Meanwhile, avalanche breakdown phenomenon has provided an ultimate high‐gain route toward photodetection in the form of single‐photon detectors. Here, the authors report ultrasensitive avalanche phototransistors based on monolayer MoS2 synthesized by chemical vapor deposition. A lower critical field for the electrical breakdown under illumination shows strong evidence for avalanche breakdown initiated by photogenerated carriers in MoS2 channel. By utilizing the photo‐initiated carrier multiplication, their avalanche photodetectors exhibit the maximum responsivity of ≈3.4 × 107 A W−1 and the detectivity of ≈4.3 × 1016 Jones under a low dark current, which are a few orders of magnitudes higher than the highest values reported previously, despite the absence of any additional chemical treatments or photosensitizing layers. The realization of both the ultrahigh photoresponsivity and detectivity is attributed to the interplay between the carrier multiplication by avalanche breakdown and carrier injection across a Schottky barrier between the channel and metal electrodes. This work presents a simple and powerful method to enhance the performance of photodetectors based on carrier multiplication phenomena in 2D materials and provides the underlying physics of atomically thin avalanche photodetectors.

A model for avalanche breakdown calculation in low-voltage trench power MOSFET devices

In this work, the avalanche breakdown phenomenon in low-voltage trench power MOSFET is investigated through two-dimensional device simulations. The breakdown dependence from device geometrical characteristics is carefully characterized with particular attention to trench depth and drain region length and doping. An analytical model for breakdown calculation in a trench structure is presented. The analytical model is based on a well-known p+–n unilateral junction model, with a maximum electric field value correction to take into account the trench structure perturbation. It shows good results for a wide range of drift region characteristics and trench lengths.

Physical study of the avalanche breakdown phenomenon in HEMTs

The aim of this study is the physical understanding of the avalanche breakdown phenomenon in PHEMTs (AlGaAs/GaInAs/GaAs), in order to optimise the structure and to improve the breakdown voltage. It is therefore necessary to study the influence of the physical parameters on which this phenomenon depends, such as the layer structure, the doping concentration or the gate recess topology. The study is based on a two-dimensional hydrodynamic modelling, that takes electrons and holes into account, and shows that the highest breakdown voltage is obtained for a double step gate recess with two delta-doping layer plans.

Magnetic-field-controllable avalanche breakdown and giant magnetoresistive effects in Gold∕semi-insulating-GaAs Schottky diode

Gold (Au)∕semi-insulating (SI)-GaAs Schottky diode was fabricated by the standard photolithography method using wet etching. Magnetic-field-dependent avalanche breakdown phenomena were observed in the current–voltage curves measured under magnetic field. The avalanche breakdown due to impact ionization was postponed to higher electrical field under applied magnetic field. Accordingly, threshold voltages of avalanche breakdown increased with the applied magnetic field. Above 0.2T, avalanche breakdown was totally quenched. When Au-SI-GaAs Schottky diode was operated above the threshold voltage, giant mangetoresistive effects up to 100 000% were achieved under magnetic field of 0.8T.

Breakdown characteristics of emitter-base and collector-base junctions of silicon bipolar junction transistors

Recently, avalanche breakdown phenomena have received considerable attention. This is due to the lower breakdown voltage in advanced bipolar junction transistors (BJTs), which result from the increased collector doping. Avalanche breakdown in BJTs is an old issue; however, it is still not well-understood. This paper reports on studies of the breakdown characteristics of emitter-base and collector-base junctions with the other terminal open or shorted to the base. This is fundamental for the understanding of current-voltage characteristics of Si BJTs operated in the breakdown condition. The study includes the phenomena of avalanche breakdown, punchthrough and avalanche-induced light emission.

Analysis of avalanche breakdown in bipolar transistors based on majority carrier transportation

This paper describes a new analysis of the avalanche breakdown phenomenon in bipolar transistors for different bias conditions of the emitter-base junction. This analysis revolves around the transportation and storage of majority carriers in the base region. Using this analysis one can compute all the voltage–current characteristics of a transistor under avalanche breakdown.

Modeling of 0.1-µm MOSFET on SOI structure using Monte Carlo simulation technique

Simulation of a 0.1-µm MOSFET's characteristics using the Monte Carlo method is introduced in this paper. The studied device is a 0.1-µm MOSFET on an ultrathin nearly intrinsic SOI structure that is thought to be useful to suppress short-channel effects. To carry out the calculation, intravalley scattering with acoustic phonon and intervalley inelastic scattering have been taken into account in our model. Surface roughness scattering has also been considered in a particle manner using a classical model, which is a combination of both specular reflection and diffused scattering. In order to take the avalanche breakdown phenomena into account, a two-carrier many-particle Monte Carlo method has been used here. We proposed a new model for the impact ionization probability, and also for the velocity distribution of both the primary electron and the generated electron-hole pairs in this paper.

A versatile two‐dimensional device simulation program and its application to NMOS

AbstractThe versatile algorithms of two‐dimensional device simulation programs are studied in detail. We have separated the device simulator which is independent of the device structure and the user's analysis purpose, and the preprocessor that specifically deals with user interface. Moreover, the algorithms of the device simulator become the discretization by information obtained at the nodes only, electrode current definition at the nodes of electrodes, initial guess using two‐dimensional numerical depletion approximation, and the iterative operation of the device simulation by step design. Using these algorithms we developed a two‐dimensional device simulator UNISAS, and confirmed the validity of the versatile algorithm using an example of NMOS. Step design is used for the analysis of the avalanche phenomenon of NMOS. Solving for the two carriers, we have explained easily the flow of electrons and holes in the avalanche breakdown phenomenon. Moreover, by changing only input data, we have easily analyzed the five‐gate NMOS.

Electron trapping in thin SiO 2 films due to avalanche currents

The avalanche breakdown phenomenon in silicon results in the injection of charge into silicon dioxide, where it may be partly trapped. Experimental results on the dependence of electron trapping in silicon dioxide on total dose and dose rate (current density) are presented for avalanching MOS drain junctions and capacitors.

Uniform Silicon p-n Junctions. I. Broad Area Breakdown

Small area silicon p-n junctions have been made which are free from exposed edges and dislocations passing through the space-charge region. It is believed that the space-charge regions of these junctions more closely resemble plane parallel geometries than any studied similarly hitherto. The avalanche breakdown phenomena in these uniform junctions are shown to be drastically different from those occuring in junctions that contain many dislocations. A comparison is made between the uniform junctions and one that is similar except that it possesses two breakdown-inducing sites, probably dislocations. In the latter junction the reverse characteristic shows two slightly separated rapid increases in current which coincide, biaswise, with the formation of two isolated light-emitting microplasmas, the occurrence of characteristic microplasma noise, and two singularities in the charge-multiplication characteristics. The uniform junctions show no such phenomena at intermediate voltages, breakdown occurring at a voltage roughly twice that at which the microplasmas form and which was previously thought typical for the given material resistivity. The light emission pattern accompanying breakdown in the uniform junctions appears more diffuse (giving rise to the term—macroplasma) than in nonuniform junctions where it normally appears as an array of intense local spots (microplasmas). It is concluded that microplasmas are not a necessary accompaniment of avalanche breakdown in silicon, but that they tend to occur where there are field or lattice inhomogeneities.

Breakdown in Silicon pn Junctions†

ABSTRACT Some useful empirical relationships on the variation of effective ionization coefficients associated with the avalanche breakdown phenomena in pn junctions are derived from measurements on silicon alloy junctions, in the range of impurity concentrations of the basic material from 5 × 1013/cm3 to 10l8/cm3. These results show that for electric field strengths from 1.5 × 203 v/ cm to 3 × 105 v /cm the effective ionization coefficient is equal to 18E7; from 3 × 10 7 v/cm to 6 × 105 v/cm it is of the form 2.7 × 10 5 exp–(6.45/E) and for values greater than 6 × 105 v/cm the effective ionization coefficient tends to E 105/5 where in all cases E is measured in units of 105 v/cm. Some discussion is given on the compatibility of calculations of ionization coefficients derived from breakdown measurements and those from multiplication measurements.