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It is well-known that SiC crystal deficiencies are delaying the market penetration of outstandingly superior SiC power devices. Efforts to date have centred on eradicating extended defects from 4H-SiC bulk crystals and epitaxial thin films. Among the extended defects existing in these materials, basal plane stacking faults (SFs) are one of the most serious concerns in SiC power devices because they are formed during the forward-bias operation of 4H-SiC PiN diodes and detrimental to SiC power devices, such as SiC MOSFETs as well as SiC BJTs and PiN diodes. In this phenomenon, i.e., the so-called “bipolar degradation”, single Shockley-type SFs (SSSFs) expand via the recombination of minority carriers (holes) at the partial dislocations in the Si core, which encompass the SSSFs. Recombination-enhanced dislocation glide (REDG) is widely accepted as the most probable kinematic mechanism of this phenomenon, and several other kinematic and energetic effects have been discussed in conjunction with the REDG mechanism. Another negative effect of SF formation in SiC crystals is the spontaneous formation of double Shockley SFs (DSSFs) in heavily nitrogen-doped 4H-SiC crystals, which largely increases the resistivity of the crystals. When the nitrogen concentration exceeds the critical value (2–3 × 1019 cm−3), DSSFs are spontaneously formed in the crystals during high-temperature annealing (> 1100°C). DSSFs have been shown to heal (shrink) upon annealing at even higher temperatures (1800°C), and the co-doping of aluminum acceptors tends to reduce the density of DSSFs in heavily nitrogen-doped 4H-SiC crystals. The above-mentioned two phenomena can be explained based on the concept of quantum well action (QWA). In the QWA, electrons in the conduction band of 4H-SiC enter the SF-induced quantum well, consequently decreasing the electronic energy of the system. However, from the viewpoint of thermodynamics, the two phenomena differ from each other. Whereas DSSF formation is a thermodynamically equilibrium process, SSSF expansion in SiC PiN diodes occurs under non-equilibrium conditions, such as the forward biasing of the PiN diode or ultraviolet light illumination of the materials. In this respect, it is worthy to note that SSSF expansion only occurs under non-equilibrium conditions and has never been observed in thermal equilibrium even when the nitrogen concentration in 4H-SiC crystals exceeds 1 × 1020 cm−3. In this paper, I will try to clarify the physical origin of the driving force of the SSSF expansion during the forward-biasing of 4H-SiC PiN diodes via theoretical investigation of the energetics of the SF formation in 4H-SiC crystals under non-equilibrium conditions. Unified understanding of the SF expansion under thermal equilibrium and non-thermal equilibrium conditions will also be attempted based on the QWA concept. The similarity and dissimilarity in underlying physics between the SF formation in forward-biased 4H-SiC PiN diodes and that in heavily nitrogen-doped 4H-SiC crystals during high temperature annealing are discussed, taking into account the electron trapping into the SF and the resulting positive charge formation in the materials. The difference in the dimensionality of the electron systems in SFs (two-dimensions) and bulk 4H-SiC (three-dimensions) provides different energy dependencies of the density of states for electrons in the two systems and plays an important role in the temperature dependence of the SF expansion in 4H-SiC crystals.

Reduction of the performance-limiting defects in SiC epitaxial substrates is indispensable to further penetration of SiC devices into the power device markets. This paper provides an opportunity to overview the current issues in SiC epitaxial substrates, focusing on dislocation-related problems. Structural defects such as threading screw dislocations (TSDs) and basal plane dislocations (BPDs) as well as surface morphological defects on the epitaxial layers due to dislocations are of current concern. The paper reviews recent important results regarding these defects from the viewpoint of crystal growth and discusses their causes and formation mechanisms.

Wide bandgap (WBG) semiconductors, especially Silicon Carbide (SiC) and Gallium Nitride (GaN), offer unprecedented opportunities for transformative changes in electric utility and transportation infrastructures. Compared to semiconductor silicon, SiC and GaN offer significantly higher electrical and thermal conductivities, increased avalanche breakdown field strength, and improved ruggedness under extreme environmental operating conditions. These basic material properties translate into more compact and lightweight energy conversion systems with significant energy savings, much improved signal sensing and transmission characteristics, and longer operating lifetimes in the field. Commercial products that are poised to significantly benefit from SiC and GaN semiconductors include solid-state energy converters, power management electronics, power amplifiers, light-emitting diodes (LEDs), solar cells, lasers, and environmental sensors. The current global annual market potential for these products is collectively in excess of $100 billion. The potential annual market size for WBG power semiconductor devices alone now exceeds $30billionwithexponentialgrowthexpectedinthenextdecade.However, state-of-the-art commercial WBG power devices have limited voltage and current ratings, unproven field-reliability, and are prohibitively expensive. Consequently, the current global sales of WBG power devices is about $200 million per year. Realizing the current technology status and the vast commercial potential of WBG power semiconductor devices, an annual ECS Symposium on GaN and SiC Power Technologies was established in 2011. The2013Symposiumispoisedtobeveryexcitingandwillincludeoral presentations of more than 60 high-quality technical papers and two evening panel sessions involving in-depth discussion of topics ranging from materials to end-applications, and their inter-relationships, in order to understand and address the critical issues that are hindering rapid commercialization of WBG power technologies. Thisfocusissueincludesatotalof18full-lengthpeer-reviewedpapers. The focus issue begins with an overview paper that summarizes the current status and emerging trends in WBG power semiconductor devices from application considerations; the imminent need to reduce crystal defects in both bulk substrates and epitaxial layers is the highlight of this paper. There are a total of eight papers on SiC material technology.MorespecificallyonepaperonSiCbulksubstrategrowth, five papers on SiC homoepitaxy, one paper on SiC surface modification, and one paper on SiC material characterization. In addition, two papers on bulk GaN crystal growth and one paper on GaN-on-Si epitaxy are included. One paper deals with SiC and GaN wafer planarization,animportantprocessingtechniquepriortomaterialgrowth ∗ Electrochemical Society Active Member.

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