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

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

Models for the electron mobility in the three most important silicon carbide (SiC) polytypes, namely, 4H, 6H, and 3C SiC are developed. A large number of experimental mobility data and Monte Carlo (MC) results reported in the literature have been evaluated and serve as the basis for the model development. The proposed models describe the dependence of the electron mobility on doping concentration, temperature, and electric field. The low-field mobility in 4H SiC is much higher than in 6H and 3C in the doping range interesting for RF power transistors (10/sup 16/ cm/sup -3/ ...10/sup 18/ cm/sup -3/), whereas the saturation velocities in the three polytypes investigated are nearly the same (slightly above 2/spl times/10/sup 7/ cm/s at 300 K). The models developed can be easily incorporated into numerical device simulators.

Electron mobility models for 4H, 6H, and 3C SiC [MESFETs]

Wide bandgap semiconductors show promise for high-power microwave electronic devices. Primarily due to low breakdown voltage, it has not been possible to design and fabricate solid-state transistors that can yield radio-frequency (RF) output power on the order of hundreds to thousands of watts. This has severely limited their use in power applications. Recent improvements in the growth of wide bandgap semiconductor materials, such as SiC and the GaN-based alloys, provide the opportunity to now design and fabricate microwave transistors that demonstrate performance previously available only from microwave tubes. The most promising electronic devices for fabrication in wide bandgap semiconductors for these applications are metal-semiconductor field-effect transistors (MESFETs) fabricated from the 4H-SiC polytype and heterojunction field-effect transistors (HFETs) fabricated using the AlGaN/GaN heterojunction. These devices can provide RF output power on the order of 5-6 W/mm and 10-12 W/mm of gate periphery, respectively. 4H-SiC MESFETs should produce useful performance at least through X band and AlGaN/GaN HFETs should produce useful performance well into the millimeter-wave region, and potentially as high as 100 GHz.

SiC and GaN transistors - is there one winner for microwave power applications?

Grapbene, a two-dimensional sheet of sp2-bonded carbon arranged in a honaycomb lattice, is not only the building block of fullerenes, carbon nano tubes (CNTs) and graphite, it also has interesting properties, which have caused a flood of also has interesting properties white have caused a flood of activities in the past few years The possibility to grow graph-itic films with thicknesses down to a single graphene layer epitaxially on-SiC{0001} surfaces is promising for for future applications The two-dimensional nature of epitaxial graphene films make them ideal objects for surface science techniques such as photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy The present article summarizes results from recent photoemission studies covering a variety of aspects such as the growth of epitaxial graphene and few layer graphene, the electronic and structural properties of the interface to the SiC substrate, and the elecinterface to the SiC substrate, and the electronic structure of the epitaxial graphene stacks

/pdf/epitaxial-graphene-a-new-material-1leh5tdg8o.pdf

Epitaxial graphene : a new material

Silicon carbide (SiC) is an emerging semiconductor which has proven to be well suited to high temperature power switching and high-frequency power generation. This paper examines recent advances in materials development and device performance. In boule growth, we have focused on increasing boule diameter and reducing defect counts. Two conductivity types have been developed: (1) undoped semi-insulating for MESFETs, and (2) nitrogen doped highly conducting boules for SITs and power switches. Very uniform planetary multiwafer epitaxial layer growth on these wafers is described, in which specular epitaxial layers have been obtained with growth rates of 3-5 /spl mu/m/hr, exhibiting unintentional n-type doping of /spl sim/1/spl times/10/sup 15/ cm/sup -3/, and associated room temperature Hall mobilities of /spl sim/1000 cm/sup 2//Vs. Controlled n-type doping between /spl sim/5/spl times/10/sup 15/ cm/sup -3/ and >1/spl times/10/sup 18/ cm/sup -3/ has also been demonstrated using nitrogen doping. SiC finds application in high temperature power switching devices and microwave power transistors. MOS turn-off thyristors (MTO/sup TM/) are being investigated as power switches because they offer ease of turn-off, 500/spl deg/C operation and reduced cooling requirements. In the fabrication of high power, high frequency transistors at UHF, L-band, S-band and X-band, SiC has been found superior to both silicon and GaAs. For example, a 4H-SiC UHF television module has demonstrated good signal fidelity at the 2000 W PEP level, S-band transistors have shown 300 W peak power for radar applications, and 6 W power output has been obtained at X-band.

Recent advances in high temperature, high frequency SiC devices

Publisher Summary This chapter discusses the applications of silicon carbide (Sic) in high-power electronics. Most traditional integrated circuit technologies using silicon devices are not able to operate at temperatures above 250°C especially when high operating temperatures are combined with high-power, high frequency, and high-radiation environments. As an example of one such application, the more electric aircraft concept offers substantial system-level benefits that are similar to the more electric tank, more electric ship, and more electric automobile concepts. In addition to these applications, Sic has potential for use in numerous other high power, high frequency, and radiation-resistant applications. Sic, aluminum nitride (AlN), gallium nitride (GaN), boron nitride (BN), diamond, and zinc selenide (ZnSe) are the primary wide-bandgap semiconductors now being developed for use in the aforementioned applications. Doping in Sic for device fabrication is accomplished via epitaxially controlled doping and hot ion implantation. Temperatures required for diffusion are too high (>1800T) for standard device processing because of the very high bond strength possessed by Sic. The two most common dopants used in Sic are nitrogen (n-type) and aluminum (p-type), as discussed previously, although boron is sometimes used for p-type implants.

Chapter 5 SiC for Applications in High-Power Electronics

Silicon Carbide (SiC) is an emerging semiconductor that has proven itself especially well-suited to high temperature power switching and high-frequency power generation. In this paper we examine recent advances in materials development and device performance. In boule growth we have focused on increasing boule diameter and reducing defect counts. Two conductivity types have been developed (1) semi-insulating for MESFETs, and (2) highly conducting boules for SITs and power switches. Very uniform planetary multi-wafer epitaxial layer growth on these wafers is described, in which specular epitaxial layers have been obtained with growth rates of 3-5 μm h -1 exhibiting unintentional n-type doping of ∼ 1 × 10 15 cm -3 , and room temperature Hall mobilities of ∼ 1000 cm 2 V -1 s -1 . Controlled n-type doping between ∼ 5 × 10 15 cm -3 and > 1 × 10 19 cm -3 has also been demonstrated using nitrogen doping. SiC finds application in high temperature power switching devices and microwave power transistors. MOS Turn-Off Thyristors (MTO) are being investigated as power switches because they offer ease of turn-off, 500°C operation and reduced cooling requirements. In the fabrication of high-power, high-frequency transistors at UHF, L-, S-, and X-bands SiC has been found superior to both silicon and GaAs. For example, a 4H-SiC UHF television module has demonstrated good signal fidelity at the 2000 W PEP level, S-band transistor packages have shown 300 W peak power for radar applications, and 6 W power output has been obtained at X-Band.

Advances in SiC materials and devices: an industrial point of view

Wide bandgap semiconducting materials are promising candidates for high-power, high-temperature, microwave and optoelectronic devices because of their superior thermal and electrical properties in comparison to conventional semiconductors. Recent developments in SiC and GaN materials and processing have enabled the demonstration of semiconductor devices with dramatically improved performance. Examples of these developments and new wide bandgap devices are presented.

SiC and GaN wide bandgap semiconductor materials and devices

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Recent advances in high temperature, high frequency SiC devices

Chapter 5 SiC for Applications in High-Power Electronics

Advances in SiC materials and devices: an industrial point of view

SiC and GaN wide bandgap semiconductor materials and devices