Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

A Survey of Wide Bandgap Power Semiconductor Devices

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

In this review, the structural, mechanical, thermal, and chemical properties of substrates used for gallium nitride (GaN) epitaxy are compiled, and the properties of GaN films deposited on these substrates are reviewed. Among semiconductors, GaN is unique; most of its applications uses thin GaN films deposited on foreign substrates (materials other than GaN); that is, heteroepitaxial thin films. As a consequence of heteroepitaxy, the quality of the GaN films is very dependent on the properties of the substrate—both the inherent properties such as lattice constants and thermal expansion coefficients, and process induced properties such as surface roughness, step height and terrace width, and wetting behavior. The consequences of heteroepitaxy are discussed, including the crystallographic orientation and polarity, surface morphology, and inherent and thermally induced stress in the GaN films. Defects such as threading dislocations, inversion domains, and the unintentional incorporation of impurities into the epitaxial GaN layer resulting from heteroepitaxy are presented along with their effect on device processing and performance. A summary of the structure and lattice constants for many semiconductors, metals, metal nitrides, and oxides used or considered for GaN epitaxy is presented. The properties, synthesis, advantages and disadvantages of the six most commonly employed substrates (sapphire, 6H-SiC, Si, GaAs, LiGaO 2 , and AlN) are presented. Useful substrate properties such as lattice constants, defect densities, elastic moduli, thermal expansion coefficients, thermal conductivities, etching characteristics, and reactivities under deposition conditions are presented. Efforts to reduce the defect densities and to optimize the electrical and optical properties of the GaN epitaxial film by substrate etching, nitridation, and slight misorientation from the (0 0 0 1) crystal plane are reviewed. The requirements, the obstacles, and the results to date to produce zincblende GaN on 3C-SiC/Si(0 0 1) and GaAs are discussed. Tables summarizing measures of the GaN quality such as XRD rocking curve FWHM, photoluminescence peak position and FWHM, and electron mobilities for GaN epitaxial layers produced by MOCVD, MBE, and HVPE for each substrate are given. The initial results using GaN substrates, prepared as bulk crystals and as free-standing epitaxial films, are reviewed. Finally, the promise and the directions of research on new potential substrates, such as compliant and porous substrates are described.

Substrates for gallium nitride epitaxy

Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.

https://ieeexplore.ieee.org/ielaam/41/8031005/7815312-aam.pdf

Review of Silicon Carbide Power Devices and Their Applications

Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600?1700 V) SiC Schottky barrier diodes (SBDs) and power metal?oxide?semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.

https://iopscience.iop.org/article/10.7567/JJAP.54.040103/pdf

Material science and device physics in SiC technology for high-voltage power devices

SiC electronic device technology has made rapid progress during the past decade In this paper, we review the evolution of SiC power MOSFETs between 1992 and the present, discuss the current status of device development, identify the critical fabrication issues, and assess the prospects for continued progress and eventual commercialization

Status and prospects for SiC power MOSFETs

Reliability and performance limitations in SiC power devices

The present state of SiC power Schottky and PiN diodes are presented in this paper. The design, fabrication, and characterization of a 130 A Schottky diode, 4.9 kV Schottky diode, and an 8.6 kV 4H-SiC PiN diode, which are considered to be significant milestones in the development of high power SiC diodes, are described in detail. Design guidelines and practical issues for the realization of high-power SiC Schottky and PiN diodes are also presented. Experimental results on edge termination techniques applied to newly developed, extremely thick (e.g., 85 and 100 /spl mu/m) 4H-SiC epitaxial layers show promising results. Switching and high-temperature measurements prove that SiC power diodes offer extremely low loss alternatives to conventional technologies and show the promise of demonstrating efficient power circuits. At sufficiently high on-state current densities, the on-state voltage drop of Schottky and PiN diodes have been shown to be comparable to those offered by conventional technologies.

SiC power Schottky and PiN diodes

A silicon carbide metal-insulator semiconductor field effect transistor having a u-shaped gate trench and an n-type silicon carbide drift layer. A p-type region is formed in the silicon carbide drift layer and extends below the bottom of the u-shaped gate trench so as to prevent field crowding at the corner of the gate trench. A unit cell of a metal-insulator semiconductor transistor having a bulk single crystal silicon carbide substrate of n-type conductivity silicon carbide. A first epitaxial layer of n-type conductivity silicon carbide and a second epitaxial layer of p-type conductivity silicon carbide formed on the first epitaxial layer. A first trench is formed which extends downward through the second epitaxial layer and into the first epitaxial layer. A second trench, adjacent the first trench, is also formed extending downward through the second epitaxial layer and into the first epitaxial layer. A region of n-type conductivity silicon carbide is formed between the first and second trenches and having an upper surface opposite the second epitaxial layer. An insulator layer is formed in the first trench where the upper surface of the gate insulator layer formed on the bottom of the first trench is below the lower surface of the second epitaxial layer. A region of p-type conductivity silicon carbide is formed in the first epitaxial layer below the second trench. Gate and source contacts are formed in the first and second trenches respectively and a drain contact is formed on the substrate. Preferably the gate insulator layer is an oxide such that the transistor formed is a metal-oxide field effect transistor.

Silicon carbide metal-insulator semiconductor field effect transistor

The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions.

/pdf/sic-power-diodes-provide-breakthrough-performance-for-a-wide-18sxae8sx9.pdf

Ranbir Singh

Papers

Status and prospects for SiC power MOSFETs

Reliability and performance limitations in SiC power devices

SiC power Schottky and PiN diodes

Silicon carbide metal-insulator semiconductor field effect transistor

SiC power diodes provide breakthrough performance for a wide range of applications