High Power Semiconductor Devices Research Articles

Design and Development of a Compact All-Solid-State High-Frequency Picosecond-Pulse Generator

The Marx circuit structure based on fast high-power semiconductor devices is the classical way of generating picosecond pulses. However, most reported studies suggest that as the number of stages in the Marx circuit increases, the output pulse amplitude tends to saturate. This has of late made high-voltage picosecond-pulse generation a challenge. In this paper, as the number of stages increases, the internal resistance of the avalanche transistor tends to decrease with increasing current flowing through the avalanche transistor. A step-by-step wiring and debugging of the avalanche transistor-based Marx circuit demonstrates this experimentally. That is, for a certain range in the number of stages, saturation of the output pulse amplitude for the Marx circuit of avalanche transistors is not apparent. Introducing a parallel structure for the transistors not only increases the current level of the entire circuit but also further reduces the equivalent resistance of the avalanche transistors, thereby improving the output efficiency. Drawing on microstrip transmission theory, and combining the Marx circuit and avalanche transistor parallel structure, component parameters and circuit topology of the picosecond-pulse generator were redesigned, and a 30-level Marx circuit with a parallel structure of two avalanche transistors was developed. The picosecond-pulse generator outputs a pulse with adjustable voltage amplitude of 0.9–3.1 kV, a 350-ps full-width at half-maximum, a 150-ps rise time, and an adjustable high-stability repetition rate of up to 10 kHz. The number of pulses is precisely controlled. The generator is an all-solid-state compact device with high frequency suitable for research needs.

In Operando Micro-Raman Three-Dimensional Thermometry with Diffraction-Limit Spatial Resolution for GaN -based Light-Emitting Diodes

The three-dimensional (3D) temperature distribution can affect the efficiency, performance, and long-term stability of high-power semiconductor devices. Typical characterization techniques can only probe a surface, in two dimensions---a major limitation. This study uses a ``split time window'' method for Raman spectroscopy to perform 3D temperature profiling in a working high-power LED, achieving both high spatial resolution and accuracy. This $i\phantom{\rule{0}{0ex}}n$ $o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}o$ thermometry method will be very useful for revealing often-complicated device performance issues, such as efficiency droop in LEDs or current-induced degradation in lasers or power electronics.

Analysis of the Features of Hot-Carrier Degradation in FinFETs

For the first time, hot-carrier degradation (HCD) is simulated in non-planar field-effect transistors with a fin-shaped channel (FinFETs). For this purpose, a physical model considering single-carrier and multiple-carrier silicon–hydrogen bond breaking processes and their superpositions is used. To calculate the bond-dissociation rate, carrier energy distribution functions are used, which are determined by solving the Boltzmann transport equation. A HCD analysis shows that degradation is localized in the channel region adjacent to the transistor drain in the top channel-wall region. Good agreement between the experimental and calculated degradation characteristics is achieved with the same model parameters which were used for HCD reproduction in planar short-channel transistors and high-power semiconductor devices.

Анализ особенностей деградации, вызываемой горячими носителями, в транзисторах с каналом в форме плавника

AbstractFor the first time, hot-carrier degradation (HCD) is simulated in non-planar field-effect transistors with a fin-shaped channel (FinFETs). For this purpose, a physical model considering single-carrier and multiple-carrier silicon–hydrogen bond breaking processes and their superpositions is used. To calculate the bond-dissociation rate, carrier energy distribution functions are used, which are determined by solving the Boltzmann transport equation. A HCD analysis shows that degradation is localized in the channel region adjacent to the transistor drain in the top channel-wall region. Good agreement between the experimental and calculated degradation characteristics is achieved with the same model parameters which were used for HCD reproduction in planar short-channel transistors and high-power semiconductor devices.

Thermodynamic Studies of β-Ga2O3 Nanomembrane Field-Effect Transistors on a Sapphire Substrate.

The self-heating effect is a severe issue for high-power semiconductor devices, which degrades the electron mobility and saturation velocity, and also affects the device reliability. On applying an ultrafast and high-resolution thermoreflectance imaging technique, the direct self-heating effect and surface temperature increase phenomenon are observed on novel top-gate β-Ga2O3 on insulator field-effect transistors. Here, we demonstrate that by utilizing a higher thermal conductivity sapphire substrate rather than a SiO2/Si substrate, the temperature rise above room temperature of β-Ga2O3 on the insulator field-effect transistor can be reduced by a factor of 3 and thereby the self-heating effect is significantly reduced. Both thermoreflectance characterization and simulation verify that the thermal resistance on the sapphire substrate is less than 1/3 of that on the SiO2/Si substrate. Therefore, maximum drain current density of 535 mA/mm is achieved on the sapphire substrate, which is 70% higher than that on the SiO2/Si substrate due to reduced self-heating. Integration of β-Ga2O3 channel on a higher thermal conductivity substrate opens a new route to address the low thermal conductivity issue of β-Ga2O3 for power electronics applications.

Bonding Cu to Al2O3 with Bi-B-Zn Oxide Glass Via Oxidation–Reduction Reaction

Bonding Cu on Al2O3 is a key and difficult technology applied in high-power semiconductor devices. A method proposed in this work investigates bonding with a kind of Bi-B-Zn oxide glass powder paste as a solder. Oxidation–reduction reactions between the Cu plate and the solder took place and generated Bi metal during the joining procedure. With an increase in the joining temperature, the tensile strength increased due to the increase of Bi metal formation. The Bi metal played an important role in joining Cu and Al2O3 because of its much better wettability on Cu than that of the oxides. A compound ZnAl2O4 was observed to form between the Al2O3 ceramic and oxide layer, which strengthened the bond.

In-situ synthesis of co-continuous aluminum-aluminum nitride composites by arc plasma induced accelerated displacement reaction

We investigate in-situ formation of co-continuous aluminum (Al)-aluminum nitride (AlN) composites with attractive mechanical and thermal properties by newly developed arc plasma-induced accelerated displacement reaction (APADR). The core innovation of the process is that it combines a simple pressureless infiltration with a thermodynamically favorable displacement reaction of silicon nitride (Si3N4) and molten Al under arc-plasma induced ultra-high temperature. The fast volume displacement nitridation via APADR resulted from improved wettability and enhanced diffusion of dissolved nitrogen. Thus, within a minute of APADR, Al matrix composites (AMCs) containing AlN over 50 vol% were successfully fabricated by the infiltration of Al melt into Si3N4 particulate preforms with different particle size distributions. The microstructures of the composites exhibited co-continuous three-dimensional network structures with strong interfacial bonding and high interfacial thermal conductance, which resulted in a unique combination of relatively high flexural strength and high thermal conductivity. In particular, the AMCs containing nitrides of 73 vol% exhibited a low coefficient of thermal expansion, close to that of GaAs or GaN used for high-power semiconductor devices, which is the lowest value ever reported among the nitride reinforced AMCs. These results would give us a promising strategy for in-situ processing routes to fabricate continuous nitride reinforced AMCs with high dimensional and mechanical stability for heat spreader applications.

Ruhrpumpen invests in new manufacturing plant in India

Fracturing equipment is the core device in shale gas reservoir stimulation. As domestic shale gas exploration and development steps into deep layers, the development of fracturing technology puts forward higher requirements for relevant equipment. Electric drive is an important development direction of fracturing equipment technology. In this paper, the technical progress of electric drive fracturing equipment in China and abroad was investigated. It is shown that a high-power frequency conversion system is the key technology to determine the performance of electric drive fracturing equipment. After the adaptability of the high-power frequency conversion technology to electric drive fracturing equipment was analyzed, based on the fracturing operation of Model 2500 electric drive fracturing trucks in the Weiyuan Block of the Sichuan Basin for shale gas reservoir stimulation, electric drive and diesel-driven fracturing equipment were comparatively analyzed from the aspects of economic and technical indicators. And the following research results were obtained. First, compared with a diesel-driven fracturing truck of the same power, an electric drive fracturing truck can realize a full power coverage and a continuous adjustment of output displacement, and can better meet the operation requirements of fracturing process for a precise control of the pumping displacement, while reducing the power cost by 68% and the equipment purchase cost by 10–20%. Second, compared with the skid mounted equipment, an electric drive fracturing truck has a better transport performance, being suitable for the fracturing well sites with poor road conditions, such as loess gullies, hills and mountains. It is suggested that the following development direction of the electric drive fracturing equipment should focus on the improvement of single machine power density. In addition, it is recommended to enhance the basic studies on high-pressure and high-power semiconductor devices and make a good plan for the power demand of shale gas platform construction in advance, so as to give a better play to the operating cost advantage of electric drive fracturing equipment.

Highly Conductive Cu-Cu Joint Formation by Low-Temperature Sintering of Formic Acid-Treated Cu Nanoparticles.

Highly conductive Cu-Cu interconnections of SiC die with Ti/Ni/Cu metallization and direct bonded copper substrate for high-power semiconductor devices are achieved by the low-temperature sintering of Cu nanoparticles with a formic acid treatment. The Cu-Cu joints formed via a long-range sintering process exhibited good electrical conductivity and high strength. When sintered at 260 °C, the Cu nanoparticle layer exhibited a low resistivity of 5.65 μΩ·cm and the joints displayed a high shear strength of 43.4 MPa. When sintered at 320 °C, the resistivity decreased to 3.16 μΩ·cm and the shear strength increased to 51.7 MPa. The microstructure analysis demonstrated that the formation of Cu-Cu joints was realized by metallurgical bonding at the contact interface between the Cu pad and the sintered Cu nanoparticle layer, and the densely sintered layer was composed of polycrystals with a size of hundreds of nanometers. In addition, high-density twins were found in the interior of the sintered layer, which contributed to the improvement of the performance of the Cu-Cu joints. This bonding technology is suitable for high-power devices operating under high temperatures.

Heatsink diamond nanostructures for microwave semiconductor electronics

A basic technique for manufacturing and processing polycrystalline diamond as a promising material for heatsinks of high-power microwave semiconductor devices is proposed. The fabrication of polycrystalline diamond wafers by chemical vapor deposition is investigated. The choice of a method for fragmenting polycrystalline diamond wafers is considered and a new technique for low-pressure laser/plasma chemical cutting of wafers in a gaseous medium is proposed which consists of growing polycrystalline diamond on preshaped silicon substrates and subsequent silicon etching.

Thermal shock and degradation of metallization systems on silicon

Purpose The purpose of this study is to investigate the mechanisms of degradation of aluminum metallization under conditions of thermal shock caused by rectangular current pulses (amplitude j < 8 × 1010 A/m2, duration t < 800 μs). Design/methodology/approach The results were obtained using oscillography and optical microscopy and through the construction of an empirical model of the thermal degradation of metallization systems. Findings Initially, for the authors’ studies, they deduced an equation that associated the depth of melting with the parameters of a current pulse. Research limitations/implications The authors were able to observe effects only in systems with appropriate adhesion of the thin metal films. For the systems with bad adhesion, the main mechanisms of degradation were associated with the melting of the metal, the formation of melted drops (up to 20 mcm in size) and the movement of these drops along the electrical field due to the electrocapillary effect. Practical/implications The mechanisms the authors studied could only occur in high-power semiconductor devices. Originality/value The principal mechanism of melting of a metallization track is linked to the heat dissipation at the interface of solid and liquid phases under conditions of thermal shock. The authors estimated the mechanical stresses in subsurface layers of silicon in the proximity of a non-stationary thermal source. The authors’ results show that the mechanical stresses that are strong enough to form dislocations emerge with current flow with power measuring approximately 0.7 Pkr.

Investigation of Electric Field Induced Ion Migration in Semiconductor Encapsulation Materials without the Interference of Electron Conductivity

Ion migration can cause severe damage to high power semiconductor devices. One of the main sources of mobile ions is the encapsulation material such as molding compounds. Within this work a method will be described to evaluate the risk of field induced ion migration of different molding compounds depending on the temperature and field strength. This method allows the qualitative and quantitative determination of ion mobility in molding compounds, without the interference of electron conductivity.

Die-attaching silver paste based on a novel solvent for high-power semiconductor devices

A new solvent composed of 4-(tert-butyl) cyclohexyl acetate as a dilute agent and HPMDA as a thickener was developed to make micron-sized Ag paste and to bond power semiconductors. The new Ag paste achieved sentinel printing to form sharp Ag patterns with uniform thickness and defined boundaries, which is a key to printing fine pitches in the electronics industry. The electrical resistivity of Ag patterns of 3 μΩ cm was obtained at 280 °C for 30 min. Two Ag-plating copper substrates were successfully bonded with the new Ag paste and the shear strength gradually increased with the bonding temperature. A high strength of 80 MPa was achieved at 280 °C under a small sintering pressure of 0.4 MPa. This value is far higher than the value obtained by using an expensive Ag nanoparticle paste. The detailed mechanism is discussed in this work by comparison with common ethylene glycol solvent.

Thermoelectric models of high-power bipolar semiconductor devices. Part II. Nonlinear model of LEDs

A thermoelectric model of a high-power heterojunction LED is developed, and the distributions of temperature and current density in the LED structure are obtained with allowance for several effects of thermal feedback. It is demonstrated that the dependence of the quantum efficiency on the current density and temperature leads to a significant nonuniformity of the temperature and current-density distributions in the LED structure. The calculated results are proven by the experimental dependences of the junction–housing thermal resistances of particular LEDs on the current. The Comsol Multiphysics simulation medium is interactively involved in the calculation and analysis of the temperature and current-density distributions in the LED structure with a thermophysical macrodefect in the approximation of the local thermal feedback. A critical size of the macrodefect that corresponds to the maximum nonuniformity of the thermal distribution is obtained.

Thermoelectric models of high-power bipolar semiconductor devices. Part I. Model of a high-frequency transistor with defects

A generalized thermoelectric model of a bipolar semiconductor device that takes into account thermoelectric feedback and the presence of various macrodefects is proposed. It is used to develop thermoelectric models of high-frequency high-power bipolar transistor (PBT) with electrophysical and thermophysical defects. The dependences of the maximum overheating of the working surface of crystal on the defect size and position are obtained. It is demonstrated that the temperature dependence of the power density emitted in the PBT structure leads to a nonlinear dependence of the maximum and mean temperatures of the crystal surface on the PBT power consumption. The calculated results are in reasonable agreement with the experimental dependences of the junction—housing thermal resistances of particular PBTs on the scattered power.

Loss Analysis and Comparison of High Power Semiconductor Devices in 5MW PMSG MV Wind Turbine Systems

This paper provides a loss analysis and comparison of high power semiconductor devices in 5MW Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) Wind Turbine Systems (WTSs). High power semiconductor devices of the press-pack type IGCT, module type IGBT, press-pack type IGBT, and press-pack type IEGT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on the back-to-back type 3-level Neutral Point Clamped Voltage Source Converters (3L-NPC VSCs) supplied from a grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through a loss analysis considering both the conduction and switching losses under the operating conditions of 5MW PMSG wind turbines, particularly for application in offshore wind farms. This paper investigates the loss analysis and thermal performance of 5MW 3L-NPC wind power inverters under the operating conditions of various power factors. The loss analysis and thermal analysis are confirmed through PLECS Blockset simulations with Matlab Simulink. The comparison results show that the press-pack type IGCT has the highest efficiency including the snubber loss factor.

공장 전기 설치를 위한 휴대용 전력품질 모니터링 시스템

Abstract High-power semiconductor devices and microprocessors in factory electrical installation so sensitive to power quality measurements such as harmonic currents, voltage fluctuations, flicker, current imbalance. Therefore, the little change of power quality can influences the productivity of factory electrical machines. Troubleshooting these problems requires accurate measurements and analysis of power quality with monitoring instruments that can effectively locate issues and identify solutions. In this paper, the author presents hand-held power quality monitoring system to locate issues and identify solutions. The proposed system consists of two parts, One is to develop hand-held power meters by using NI(National Instrument) DAQ(Data Acquisition) and WLAN. Another is develop power quality monitoring MMI(Man-Machine Interface) using LabView software. To demonstrate the validity of the proposed algorithm, variable tests are carried out. Key Words : Hand-held, Power meter, Power quality, Electrical machines, Monitoring system

Robust Double-Ring Junction Termination Extension Design for High Voltage Power Semiconductor Devices Based on 4H-SiC

In this study, a new robust double-ring junction-termination-extension (DR-JTE) for high-voltage pn-diodes is presented and analyzed using numerical simulations. As figured out, the DR-JTE reduces the electrical field at both, the edge of the single-JTE region and the MESA-transition, respectively. Thereby, due to the reduction of the electrical field, the maximum breakdown voltage is increased to 91.5% of the theoretical, parallel-plane breakdown voltage of 6.5kVand the maximum acceptable deviation of the optimum implantations dose is twice than that of the single-JTE structure. Furthermore, due to the internal ring, the MESA-transition is shielded from the electrical field and therefore the breakdown voltage is much less affected by the angle of the MESA.

Thermal Regime of High-power Laser Diodes

We discuss the design and application perspectives of different crystal, ceramic and composite-type submounts with thermo-compensating properties as well as submounts from materials with high thermal conductivity for overcoming thermal problem in high-power laser diodes (LD) and improving thermal management of other high-power optoelectronic and electronic semiconductor devices. Thermal fields in high-power laser diodes were calculated in 3 D thermal model at CW operation for some heatsink designs taking into account the experimental dependence of laser total efficiency against pumping current in order to extend the range of reliable operation up to thermal loads 20-30W and corresponding output optical power up to 15-20W for 100μm stripe laser diodes.

The Research of LEDs with Metal Substrates

There are good thermal conductivity, high luminous efficiency in the LEDs with metal substrates, which can effectively solve the problems such as poor heat dissipation、poor reliability of LEDs. The copper substrate LEDs have successfully developed with good performance by SemiLEDs, which indicates the direction of the high-power semiconductor devices for lighting.