Breakdown Limit Research Articles

Understanding the Leakage Mechanisms and Breakdown Limits of Vertical GaN-on-Si p+n−n Diodes: The Road to Reliable Vertical MOSFETs

This work investigates p+n−n GaN-on-Si vertical structures, through dedicated measurements and TCAD simulations, with the ultimate goal of identifying possible strategies for leakage and breakdown optimization. First, the dominant leakage processes were identified through temperature-dependent current–voltage characterization. Second, the breakdown voltage of the diodes was modelled through TCAD simulations based on the incomplete ionization of Mg in the p+ GaN layer. Finally, the developed simulation model was utilized to estimate the impact of varying the p-doping concentration on the design of breakdown voltage; while high p-doped structures are limited by the critical electric field at the interface, low p-doping designs need to contend with possible depletion of the entire p-GaN region and the consequent punch-through. A trade-off on the value of p-doping therefore exists to optimize the breakdown.

The statistics of electron–hole avalanches

Charge multiplication through avalanche processes is commonly employed in the detection of single photons or charged particles in high-energy physics and beyond. In this report, we provide a detailed discussion of the properties of avalanches driven by two species of charge carriers, e.g. electrons and holes in a semiconductor exposed to an electric field. We derive equations that describe the general case of avalanches developing in position-dependent electric fields and give their analytical solutions for constant fields. We discuss consequences for the time resolution achievable with detectors that operate above the breakdown limit, e.g. single-photon avalanche diodes (SPADs) and silicon photomultipliers (SiPMs). Our results also describe avalanches that achieve finite gain and are important for avalanche photodiodes (APDs) and low-gain avalanche detectors (LGADs).

Deep learning-enabled prediction of 2D material breakdown

Characterizing electrical breakdown limits of materials is a crucial step in device development. However, methods for repeatable measurements are scarce in two-dimensional materials, where breakdown studies have been limited to destructive methods. This restricts our ability to fully account for variability in local electronic properties induced by surface contaminants and the fabrication process. To tackle this, we implement a two-step deep-learning model to predict the breakdown mechanism and breakdown voltage of monolayer MoS2 devices with varying channel lengths and resistances using current measured in the low-voltage regime as inputs. A deep neural network (DNN) first classifies between Joule and avalanche breakdown mechanisms using partial current traces from 0 to 20 V. Following this, a convolutional long short-term memory network (CLSTM) predicts breakdown voltages of these classified devices based on partial current traces. We test our model with electrical measurements collected using feedback-control of the applied voltage to prevent device destruction, and show that the DNN classifier achieves an accuracy of 79% while the CLSTM model has a 12% error when requiring only 80% of the current trace as inputs. Our results indicate that information encoded in the current behavior far from the breakdown point can be used for breakdown predictions, which will enable non-destructive and rapid material characterization for 2D material device development.

Characteristics of a multi-component MgO-based bioceramic coating synthesized in-situ by plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) has held great potential for the advancement of biodegradable implants, as it helps in developing porous bioceramic coatings on the surface of magnesium alloys. In this research work, MgO-based bioceramic coatings containing the Si, P, Ca, Na, and F elements have been successfully fabricated on an AZ31 magnesium alloy plate utilizing the PEO method. The characteristic current-voltage behavior of the samples during the process was surveyed in an electrolyte containing Ca(H 2 PO 4 ) 2 , Na 2 SiO 3 ·9H 2 O, Na 3 PO 4 ·12H 2 O, NaF, and KOH with a pH of 12.5 and electrical conductivity of 20 mS/cm. The results revealed that applying a voltage of 350–400 V (that is 50–100 V higher than the breakdown limit) could greatly facilitate the synthesis of a PEO ceramic coating with fewer defects and more uniform morphology. The resulting coating was a compositionally graded bioceramic layer with a thickness in the range of 3.5 ± 0.4 to 6.0 ± 0.7 µm, comprising the above-mentioned elements as promising bioactive agents. The synthesized ceramic features were investigated in terms of the elemental distribution of components through the thickness, which indicated a gradual rise in the Si and P contents and, conversely, a decline in the F content towards the outer surface. The growth mechanism of the PEO coating has been discussed accordingly.

Electric Field and DC Breakdown Voltage of Multi-layer Dielectrics in Parallel-Plane Geometry

In this paper, the electric field, space charge and temperature distributions across a double layered dielectric are investigated under DC voltage. The dissimilarity of material properties of different layers, the effect of electric field and temperature dependent conductivity are found to play critical role in the electro-thermal problem of multi-dielectrics. At the interface, Maxwell-Wagner polarization is incorporated for electric field and interfacial charge, while temperature is considered as a continuous function of space inside the material. The current continuity equation, thermal continuity equation and Poisson's equation are simultaneously solved using numerical methods in parallel-plane electrode geometry. The electric field distribution, temperature distribution, space charge distribution and thermal breakdown limits are obtained at various boundary temperatures for different thickness proportions of layers.

Nanoscale ordering of planar octupolar molecules for nonlinear optics at higher temperatures

We develop scenarios for orientational ordering of an in-plane system of small flat octupolar molecules at the low-concentration limit, aiming towards nonlinear-optical (NLO) applications at room temperatures. The octupoles interact with external electric poling fields and intermolecular interactions are neglected. Simple statistical-mechanics models are used to analyze the orientational order in the very weak poling limit, sufficient for retrieving the NLO signals owing to the high sensitivity of NLO detectors and measurement chains. Two scenarios are discussed. Firstly, the octupolar poling field is imparted by a system of point charges; the setup is subject to cell-related constraints imposed by mechanical strength and dielectric breakdown limit. The very weak octupolar order of benchmarking TATB molecules is shown to emerge at Helium temperatures. The second scenario addresses the dipoling of octupolar molecules with a small admixture of electric dipolar component. It requires a strong field regime to become effective at Nitrogen temperature range. An estimation of the nonlinear susceptibility coefficient matrix for both scenarios is done in the high-temperature (weak interaction) limit formalism. We argue that moderate modifications of the system like, e.g., an increase of the size of the octupole, accompanied by dipole-assisted octupoling, can increase the poling temperature above Nitrogen temperatures.

Contact Charge Transfer between Nominally Identical Materials

AbstractDifferences in concentrations of excited electrons arising from geometry‐dependent differences in de‐excitation paths lead to differences in Fermi energies, which enable contact charge transfer between otherwise identical solids of different size. This model is used with a quasi‐equilibrium description of the Fermi energy to estimate a lower bound of the magnitude of charging of pairs of like particles and the charge distribution in groups of interacting like particles. The predictions agree with observed charge transfer directions between large and small particles and with the broad particle size range over which charging is observed. Estimates of charging are compared to available measurements, the breakdown limits of air, and the relative strengths of interparticle electrostatic and gravitational forces. The influence of particle size distribution on the charge distribution in groups of particles is examined.

Electrocaloric cooling over high device temperature span

Summary Electrocaloric cooling demonstrates direct electricity utilization and high energy efficiency, and is often proposed as an environmentally benign, solid-state alternative to the conventional vapor compression cooling technology. As a result, the fabrication of effective electrocaloric materials and engineering of electrocaloric cooling devices have attracted increasing attention in the cooling community. However, the limited material adiabatic temperature change under safe operation field poses a major challenge to practical electrocaloric cooling device development, since real-world applications usually require device temperature span over 20 K. This perspective presents recent efforts devoted to design electrocaloric cooling devices based on active heat regeneration and cascading approaches; both strategies have achieved significant device temperature lift ~10 K with adiabatic temperature change of 2~3 K. The strategies discussed in this work are broadly applicable to the design of efficient and compact cooling systems.

Temperature-Dependent Field Emission and Breakdown Measurements Using a Pulsed High-Voltage Cryosystem

Field emission and vacuum breakdown limit performance in many classes of electronic devices, including rf systems in particle accelerators. Although there are general explanations of both processes, a large correction factor is systematically needed to explain observations, and experimental evidence to establish the breakdown mechanism is limited. This study elucidates both issues, using a high-voltage electrode system that can operate down to cryogenic temperatures. Measurements of temperature-dependent field emission and breakdown with this system reveal remarkable effects that yield insight into both processes, which in turn will enable further development of high-field technology.

Challenges to overcome breakdown limitations in lateral β-Ga2O3 MOSFET devices

In this work, the fabrication of high-performance metal-oxide-semiconductor field-effect transistors (MOSFETs) on Si-doped homoepitaxial layers on (100) Mg-doped semi-insulating β-Ga2O3 substrates is demonstrated. Furthermore, the influence of additional gate and source field-plates is analyzed in regards to the breakdown properties of the MOSFET devices. The comparative study reveals comparable transistor performances of devices with and without field-plates showing maximum drain currents, on/off-current ratios and ON-resistances of ~75 mA/mm, 109 and 110 Ω∙mm, respectively. Moreover, both MOSFET structures show comparable breakdown voltages at around 1200 V which equals an average breakdown field strength of 2 MV/cm emphasizing no influence of the field-plates on the breakdown properties. Analysis of the thin film composition by secondary ion mass spectrometry on the processed β-Ga2O3 wafers indicates an increased concentration of silicon dopants at the interface between epitaxial layer and substrate. Our findings suggest that this might be the current main limitation factor in reaching higher breakdown voltages using field-plated β-Ga2O3 MOSFET devices.

A CMOS Data Transfer System Based on Planar RF Coupling for Reinforced Galvanic Isolation with 25-kV Surge Voltage and 250-kV/µs CMTI

This paper exploits an effective approach to overcome the breakdown limitations of traditional galvanic isolators based on chip-scale isolation barriers, thus achieving a very high isolation rating (i.e., compliant with the reinforced isolation requirements). Such an approach is based on radio frequency (RF) planar coupling between two side-by-side co-packaged chips. Standard packaging along with proper assembling techniques can be profitably used to go beyond 20-kV surge voltage without using expensive or exotic isolation components. As a proof of concept, a bidirectional data transfer system based on RF planar coupling able to withstand an isolation rating as high as 25 kV has been designed in a low-cost standard 0.35-µm CMOS technology. Experimental measurements demonstrated a maximum data rate of 40 Mbit/s using a carrier frequency of about 1 GHz. The adopted approach also guarantees a common mode transient immunity (CMTI) of 250 kV/µs, which is a first-rate performance in view of next generation galvanic isolators for wide-bandgap power semiconductor devices, such as gallium nitride high-electron mobility transistors (GaN HEMTs) and silicon carbide (SiC) MOSFETs.

Inductor-Free Output Multiplier for Power Promotion and Management of Triboelectric Nanogenerators toward Self-Powered Systems.

The output voltage of triboelectric nanogenerators (TENGs) is much higher than the overload capacity of most commercial electronics, making it hard to power them directly; so the power-management solution is indispensable. In the meanwhile, it is critical for practical applications to enhance the output performance of the TENG toward its breakdown limit, which is usually ignored before. Here, an inductor-free output multiplier (OM) for power promotion and management of TENGs is proposed, with the breakdown effect considered. This OM, as expanded based on bennet's doubler, is theoretically studied and experimentally demonstrated to significantly enhance the output performance of the TENG within only a few working cycles. The charge output was enhanced by 7.6 times experimentally with the OM. An external capacitor and a switch are applied to realize a high energy extraction ratio of up to 196%, with the average charge output per cycle of ∼3-3.75 μC achieved. This OM circuit with the smart switch is suitable for power promotion of TENGs with variable capacitance and for power management of all TENGs. The OM circuit is demonstrated to ensure the high output performance of TENGs even at a low triboelectric charge density, which is crucial for broad applications of the TENG toward self-powered systems, potentially to be a solution for improving the output performance of TENGs working in harsh environments.

Nonequilibrium statistical theoretical analysis method of TDDB of gate oxide

As one of the important factors affecting the reliability of Complementary metal oxide semiconductor integrated circuits, the time-dependent dielectric breakdown of gate oxide has always been the focus of domestic and foreign scientists. The previous researches have shown that when the electrons pass through the silicon dioxide lattice and collide with it, part of their kinetic energy will be dissipated, then among of which can create some sort of defects that behave as electron traps. However, when the electron traps density reaches a critical value in the gate oxide, the destructive thermal effects open a low-resistance ohmic path between the electrodes, thus, triggering the breakdown conducting mechanism. In this paper, in order to employing a statistical theoretical analysis method, the behavior related with time-dependent dielectric breakdown of gate oxide was investigated in detail. The following useful results are obtained, (i) According to the microscopic mechanism of the time-dependent dielectric breakdown of gate oxide under electrical stresses associated with the randomness and irreversibility of the electron traps generation in gate oxide, a theoretical analysis method has been proposed, which is based on the equation of the electron traps generation rate combined with the Langevin equation in random theory and the Fokker-Planck equation in the non-equilibrium statistical theory. (ii) In light of the dynamic equilibrium model, the generation rate equations of electron traps under constant current stress and constant voltage stress as well as the probability density distribution functions of electron traps density were determined. By integrating these distribution function, the cumulative failure rate was further obtained. (iii) Taking the specific metal oxide semiconductor capacitors as examples, the relationship between the most probable lifetime of the gate oxide and the constant current stress, constant voltage stress, as well as its thickness have been revealed. And the concept of "breakdown limit" was defined by analogy with the concept of "fatigue limit" in the phenomenon of solid fracture. (iv) The dependence of the cumulative failure rate on the current stress, voltage stress, and time has been presented. A characteristic value of the time was introduced to indicate the time when the cumulative failure rate reaches 0.63. At this time, most devices have breakdown failure. Besides, the test parameters are not affected by previous failures, and they are close to that of the cumulative failure rate of 1. The results show that the probability density distribution function of electron traps density satisfies lognormal distribution, and the obtained distribution of failures fits well with the experimental statistical data.

High-Power Wire Bonded GaN Rectifier for Wireless Power Transmission

A novel wire bonded GaN rectifier for high-power wireless power transfer (WPT) applications is proposed. The low breakdown voltage in silicon Schottky diodes limits the high-power operations of microwave rectifier. The proposed microwave rectifier consists of a high breakdown voltage GaN rectifying element for high-power operation and a novel low loss impedance matching technique for high efficiency performance. Wire bonding method is adopted to provide electrical connection between GaN chip and board which induces undesirable inductance. In order to realize high efficiency performance, an impedance matching network is proposed to exploit the unavoidable inductance along with a single shunt capacitor, resulting in a low loss matching circuit to achieve a compact high-power rectifier. The fabricated GaN rectifier exhibits a good performance in the high-power region and can withstand up to 39 dBm input power before reaching the breakdown limit at the operating frequency of 0.915 GHz and load resistance of 100 Ω. It has a compact size and exhibits high efficiency performance in high-power region (achieved a maximum efficiency of 61.2% at 39 dBm), making it suitable for high-power applications like future unmanned intelligent devices and WPT in space applications.

Tuning Thermal Transport Through Atomically Thin Ti3C2Tz MXene by Current Annealing in Vacuum

AbstractHeat transport across vertical interfaces of heterogeneous 2D materials is usually governed by the weak Van der Waals interactions of the surface‐terminating atoms. Such interactions play a significant role in thermal transport across transition metal carbide and nitride (MXene) atomic layers due to their hydrophilic nature and variations in surface terminations. Here, the metallicity of atomically thin Ti3C2Tz MXene, which is also verified by scanning tunneling spectroscopy for the first time, is exploited to develop a self‐heating/self‐sensing platform to carry out direct‐current annealing experiments in high (<10−8 bar) vacuum, while simultaneously evaluating the interfacial heat transport across a Ti3C2Tz/SiO2 interface. At room temperature, the thermal boundary conductance (TBC) of this interface is found, on average, to increase from 10 to 27 MW m−2 K−1 upon current annealing up to the breakdown limit. In situ heating X‐ray diffraction and X‐ray photo‐electron spectroscopy reveal that the TBC values are mainly affected by interlayer and interface spacing due to the removal of absorbents, while the effect of surface termination is negligible. This study provides key insights into understanding energy transport in MXene nanostructures and other 2D material systems.

Ultrafast photonic micro-systems to manipulate hard X-rays at 300 picoseconds

Time-resolved and ultrafast hard X-ray imaging, scattering and spectroscopy are powerful tools for elucidating the temporal and spatial evolution of complexity in materials. However, their temporal resolution has been limited by the storage-ring timing patterns and X-ray pulse width at synchrotron sources. Here we demonstrate that dynamic X-ray optics based on micro-electro-mechanical-system resonators can manipulate hard X-ray pulses on time scales down to 300 ps, comparable to the X-ray pulse width from typical synchrotron sources. This is achieved by timing the resonators with the storage ring to diffract X-ray pulses through the narrow Bragg peak of the single-crystalline material. Angular velocities exceeding 107 degrees s−1 are reached while maintaining the maximum linear velocity well below the sonic speed and material breakdown limit. As the time scale of the devices shortens, the devices promise to spatially disperse the temporal width of X-rays, thus generating a temporal resolution below the pulse-width limit.

In-situ real-time monitoring of spurious modes in HE11 transmission lines using multi-hole couplers in miter bends

Transmission of high-power millimeter waves for ECRH is often realised with oversized corrugated circular waveguides. Coupling from the gyrotron source to the waveguide is typically done via matching mirrors in free space. Small alignment errors of the system lead to the excitation of higher-order modes inside the waveguide beside the main transmission mode HE11. Those modes have comparably higher losses and can in worst case result in local fields exceeding the breakdown limit of the medium inside the waveguide. For alignment control over the whole pulse duration of the gyrotron, a set of hole-array couplers placed into a miter bend mirror probes the field inside the waveguide. The arrays are designed to detect the marker modes for beam offset and tilt (LP(e=o)11 )as well as for beam waist mismatch (LP02). In addition, a main mode coupler sensitive mostly for the HE11 content is used as a power monitor. By maximizing the signal of the power monitor and minimizing the content of marker modes, a first-order optimization of the coupling from free space to the waveguide can be achieved. Signal processing of the 140 GHz information is done at kHz range after downmixing, using a frequency shifted part of the power monitor signal. As the measurement system is placed in a miter bend mirror, it can also be easily installed at various locations along the transmission line to check for possible misalignments of the waveguide connections between miter bends. Simulation and low power experimental results will be shown.

Observation and discussion of avalanche electroluminescence in GaN p-n diodes offering a breakdown electric field of 3 MV cm−1

We report on the first observation of avalanche electroluminescence resulting from band-to-band recombination (BTBR) of electron hole pairs at the breakdown limit of Gallium Nitride p-n diodes grown homo-epitaxially on single crystalline GaN substrates. The diodes demonstrated a near ideal breakdown electric field of 3 MV cm−1 with electroluminescence (EL) demonstrating sharp peaks of emission energies near and at the band gap of GaN. The high critical electric field, near the material limit of GaN, was achieved by generating a smooth curved mesa edge with low plasma damage, using etch engineering without any use of field termination. The superior material quality was critical for such a near-ideal performance. An electric field of 3 MV cm−1 recorded at the breakdown resulted in impact ionization, confirmed by a positive temperature dependence of the breakdown voltage. The spectral data provided evidence of BTBR of electron hole pairs that were generated by avalanche carrier multiplication in the depletion region.

Effectiveness of compressor machine by using overall equipment effectiveness (OEE) method

Overall equipment effectiveness (OEE) is performance measure for machine/equipment effectiveness [1]. The effectiveness of machine/equipment will affect the productivity. PT Y is a company engaged in crude oil and natural gas production. Various obstacles are faced by PT Y in the course of its production, one of which is the problem of the productivity from every production process. Based on historical data from September 2016 - February 2017, the percentage of compressor's breakdown is above 20%. The company wants the upper limit of machines' breakdown only reached 10% for each period of production. Therefore needed improvement through analysis of availability, performance ratio, and rate of quality product. This study also will provide corrective suggestions through the calculation of OEE. The results of the experiment with the calculation of OEE shows that the compressor still working above the standard measurement and researcher suggests to make a preventive maintenance plan.

Reservoir Geomechanics Parameters Estimation Using Well Logs and Seismic Reflection Data: Insight from Sinjhoro Field, Lower Indus Basin, Pakistan

Nowadays, the failure to understand a hydrocarbon field’s geomechanics signifies an expensive risk in several complex drilling, well completion, and exploitation processes. Thus, the precise estimation of reservoir geomechanical parameters can lessen that risk and provide benefits all the way through oil and gas field’s lifespan. Several factors like compaction of sediments, lithology characteristics, overburden, hydrocarbon and capillary entry pressures add substantial effects to cause of abnormal pressure and resultantly affect the well design and stability. The aim of current study is to compute geomechanical properties such as overburden pressure and vertical effective stress and finally to define the lower and upper bounds (breakout and breakdown limits) of safe mud weight window by determining the pore pressure and fracture gradient for pre-drill planning in future exploration and real time monitoring in the Sinjhoro Field, the Lower Indus Basin of Pakistan. Current studies examined the wireline logs data of four wells drilled in the Cretaceous reservoir sands and seismic reflection data-based P wave velocity functions and describes a workflow for reliable estimation of geomechanical parameters. Our results revealed that high pore pressure (5000–7000 Psi) is predicated at reservoir zone and it increases in southeast directions. On the basis of pore pressure and fracture pressure, both lower (5388.89 Psi) and upper (6572 Psi) bounds for safe mud weight window are defined for safe drilling and well stability that will help future exploration and development in the Sinjhoro field. Both overburden pressure and vertical effective stress increase uniformly with depth but spatial variations are nonlinear and increasing in northwest directions. The present work will support the petroleum industry by reducing the borehole drilling cost with no compromising on environment and safety concerns.