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

Wide-bandgap semiconductors are expected to be applied to solid-state lighting and power devices, supporting a future energy-saving society. While GaN-based white LEDs have rapidly become widespread in the lighting industry, SiC- and GaN-based power devices have not yet achieved their popular use, like GaN-based white LEDs for lighting, despite having reached the practical phase. What are the issues to be addressed for such power devices? In addition, other wide-bandgap semiconductors such as diamond and oxides are attracting focusing interest due to their promising functions especially for power-device applications. There, however, should be many unknown phenomena and problems in their defect, surface, and interface properties, which must be addressed to fully exploit their functions. In this review, issues of wide-bandgap semiconductors to be addressed in their basic properties are examined toward their ?full bloom?.

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Wide-bandgap semiconductor materials: For their full bloom†

A sustainable energy future requires power electronics that can enable significantly higher efficiencies in the generation, distribution, and usage of electrical energy. Silicon carbide (4H-SiC) is one of the most technologically advanced wide bandgap semiconductor that can outperform conventional silicon in terms of power handling, maximum operating temperature, and power conversion efficiency in power modules. While SiC Schottky diode is a mature technology, SiC power Metal Oxide Semiconductor Field Effect Transistors are relatively novel and there is large room for performance improvement. Specifically, major initiatives are under way to improve the inversion channel mobility and gate oxide stability in order to further reduce the on-resistance and enhance the gate reliability. Both problems relate to the defects near the SiO2/SiC interface, which have been the focus of intensive studies for more than a decade. Here we review research on the SiC MOS physics and technology, including its brief history, the state-of-art, and the latest progress in this field. We focus on the two main scientific problems, namely, low channel mobility and bias temperature instability. The possible mechanisms behind these issues are discussed at the device physics level as well as the atomic scale, with the support of published physical analysis and theoretical studies results. Some of the most exciting recent progress in interface engineering for improving the channel mobility and fundamental understanding of channel transport is reviewed.

Silicon carbide: A unique platform for metal-oxide-semiconductor physics

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[Award for Best Review Paper Speech](30min.)Wide-Bandgap Semiconductor Materials: For Their Full Bloom

https://iopscience.iop.org/article/10.35848/1882-0786/abc787/pdf

Defect engineering in SiC technology for high-voltage power devices

Using electron paramagnetic resonance (EPR), energy levels of the carbon vacancy (V(C)) in 4H-SiC and its negative-U properties have been determined. Combining EPR and deep-level transient spectroscopy we show that the two most common defects in as-grown 4H-SiC--the Z(1/2) lifetime-limiting defect and the EH(7) deep defect--are related to the double acceptor (2-|0) and single donor (0|+) levels of V(C), respectively.

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Negative-U System of Carbon Vacancy in 4H-SiC

The authors investigated deep levels in the whole energy range of bandgap of 4H-SiC, which are generated by low-dose N+, P+, and Al+ implantation, by deep level transient spectroscopy (DLTS). Ne+-implanted samples have been also prepared to investigate the pure implantation damage. In the n-type as-grown material, the Z1∕2 (EC−0.63eV) and EH6∕7 (EC−1.6eV) centers are dominant deep levels. At least, seven peaks (IN1, IN3–IN6, IN8, and IN9) have emerged by implantation and annealing at 1000°C in the DLTS spectra from all n-type samples, irrespective of the implanted species. After high-temperature annealing at 1700°C, however, most DLTS peaks disappeared, and two peaks, IN3 and IN9, which may be assigned to Z1∕2 and EH6∕7, respectively, survive with a high concentration over the implanted atom concentration. In the p-type as-grown material, the D (EV+0.40eV) and HK4 (EV+1.4eV) centers are dominant. Two peaks (IP1 and IP3) have emerged by implantation and annealing at 1000°C, and four traps IP2 (EV+0.39eV), ...

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Detection and depth analyses of deep levels generated by ion implantation in n- and p-type 4H-SiC

Two trap-reduction processes, thermal oxidation and C+ implantation followed by Ar annealing, have been discovered, being effective ways for reducing the Z1/2 center (EC – 0.67 eV), which is a lifetime killer in n-type 4H-SiC. In this study, it is shown that new deep levels are generated by the trap-reduction processes in parallel with the reduction of the Z1/2 center. A comparison of defect behaviors (reduction, generation, and change of the depth profile) for the two trap-reduction processes shows that the reduction of deep levels by thermal oxidation can be explained by an interstitial diffusion model. Prediction of the defect distributions after oxidation was achieved by a numerical calculation based on a diffusion equation, in which interstitials generated at the SiO2/SiC interface diffuse to the SiC bulk and occupy vacancies related to the origin of the Z1/2 center. The prediction based on the proposed analytical model is mostly valid for SiC after oxidation at any temperature, for any oxidation tim...

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Analytical model for reduction of deep levels in SiC by thermal oxidation

A longest carrier lifetime of 33.2 µs was achieved by eliminating the Z1/2 center via thermal oxidation at 1400 °C for 48 h and subsequent surface passivation with a nitrided oxide on a 220-µm-thick n-type 4H-SiC epilayer. By deep-level elimination, photoluminescence (PL) in the infrared region (wavelength: 700–950 nm) was remarkably enhanced at locations of threading dislocations. A threading screw dislocation exhibited much stronger infrared PL than a threading edge dislocation. The present results indicate that carrier recombination at extended defects becomes pronounced through the elimination of the Z1/2 center in the epilayers.

https://iopscience.iop.org/article/10.1143/APEX.5.101301/pdf

Carrier Recombination in n-Type 4H-SiC Epilayers with Long Carrier Lifetimes

The Z(1/2) center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient ...

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Koutarou Kawahara

Papers

Negative-U System of Carbon Vacancy in 4H-SiC

Detection and depth analyses of deep levels generated by ion implantation in n- and p-type 4H-SiC

Analytical model for reduction of deep levels in SiC by thermal oxidation

Carrier Recombination in n-Type 4H-SiC Epilayers with Long Carrier Lifetimes

Investigation on origin of Z[1/2] center in SiC by deep level transient spectroscopy and electron paramagnetic resonance