Solid State Phenomena Vol. 393

Abstract: Silicon Carbide (SiC) is a pivotal wide-bandgap semiconductor for high-power and high-frequency electronics. However, crystalline defects, particularly Basal Plane Dislocations (BPDs), severely degrade the performance and reliability of bipolar devices by nucleating stacking faults that cause fatal forward voltage drift. This work presents the successful growth of 8-inch, 4° off-axis, n-type 4H-SiC single crystals with significantly reduced BPD density via the Physical Vapor Transport (PVT) method using an improved reactor design. The key innovation involves replacing traditional graphite components with single or polycrystalline SiC for the seed holder and guide tube, subsequently coated with a thin (10 µm) tantalum carbide (TaC) film. This design ensures thermal expansion coefficient matching and reduces thermal radiation emissivity. Etch pit density analysis revealed that the improved design reduced the overall BPD density from over 1027 cm⁻² to a remarkably low 78 cm⁻². Furthermore, it drastically improved the radial uniformity of BPD distribution by stabilizing the thermal gradient and suppressing parasitic polycrystalline nucleation, marking a critical advancement towards high-yield production of high-quality, large-diameter SiC substrates.

Abstract: The development of integrated circuits (IC) is mainly driven by the advanced processes and increased silicon wafer diameter in the past several decades. It is technically believed that the diameter of 300 mm for SiC wafer is too difficult to be achieved since SiC crystal diameter expansion is a long and tough process, the growth process of which is different from that of silicon crystal. Herein, we demonstrate the diameter expansion process of SiC crystal from 200 mm to 300 mm using physical vapor transportation (PVT) method and show the world’s first 300 mm 4H-SiC single crystal substrate with 100% 4H polytype. The driving force of crystal diameter expansion and resultant thermal stress are discussed in this paper. Based on the successful preparation of 300 mm SiC seed crystal, 12-inch high-purity, conductive n-type & p-type SiC substrates are subsequently fabricated. Quality characterization of the 300 mm SiC substrate shows very low micropipe and threading screw dislocation density below 0.05 cm^-2 and 120 cm^-2, respectively. Furthermore, both 500 μm and 750 μm thickness substrates are fabricated with bow and warp values lower than 10 μm and 30 μm, indicating high quality 300 mm substrates applicable in power devices and other emerging areas.

Abstract: 4H-SiC is a wide-bandgap semiconductor that has become essential for power electronics due to its large bandgap, high critical electric field, and excellent thermal stability. Within the {0001} basal orientation, the two polar surfaces – Si-face and C-face – exhibit distinct behaviours during chemical vapor deposition (CVD) homoepitaxy, with direct implications for device performance and manufacturing. In this work, n-type epitaxial layers were deposited on 150 mm, 4° off-axis Si-face and C-face substrates under identical conditions in a single-wafer hot-wall LP-CVD reactor (T > 1600 °C, P = 3.0 kPa, C/Si = 1.05, silane/propane/ethylene precursors, N₂ doping, HCl additive). Characterization analysis revealed pronounced polarity-dependent differences. AFM analysis showed that C-face epilayers exhibited smoother surfaces and reduced step bunching compared with Si-face layers. Optical and photoluminescence inspections show polarity-dependent defect propagation, with the C-face displaying reduced replication of extended defects under the explored conditions. However, nitrogen incorporation on the C-face orientation was more than 25× higher than Si-face orientation and displayed poor uniformity, highlighting the limited effectiveness of site-competition epitaxy on this orientation. In contrast, the Si-face provides tighter control of doping concentration and lateral uniformity, albeit with higher step bunching and rougher surfaces. These findings emphasize a fundamental trade-off in 4H-SiC homoepitaxy: the C-face offers morphological and structural advantages, while the Si-face ensures superior doping control and process stability. A deeper understanding of these polarity-dependent mechanisms is essential to optimize epitaxial growth strategies and to enable the design of high-performance SiC power devices.

Abstract: This study focuses on addressing the challenge of poor doping concentration uniformity during the epitaxial growth of 200 mm 4H-SiC substrates, which is primarily caused by difficulties in thermal field and flow field control. By systematically optimizing key process parameters, including H₂ flow rate, C/Si ratio, and growth temperature, a high uniformity concentration technology was developed. This technology has enabled a breakthrough in the performance of n-type epitaxial layers, with the doping concentration uniformity significantly improved to 0.67%. Based on the validation of this technology—encompassing 8,000 epitaxial wafers and thick epitaxial layers (≥30 μm)—the technology demonstrates excellent doping concentration uniformity. This research provides a reliable technical foundation for the large-scale application of large-size SiC materials in power devices.

Abstract: We report on the development and systematic validation of an ultra-pure silicon carbide (SiC) source material specifically engineered for physical vapor transport (PVT) growth of optical-and electronic-grade single crystals. The material is synthesized by chemical vapor deposition (CVD) using high-purity chlorosilane and methane precursors, yielding dense, void-free polycrystalline 3C-SiC with precise 1:1 stoichiometry. Over more than two years of continuous production, bulk metallic impurities across 17 monitored elements were consistently maintained below 100 parts per billion by weight (ppbw), with most batches achieving <50 ppbw. Surface metals, assessed after proprietary crushing and cleaning processes, were similarly controlled to <100 ppbw. Nitrogen levels, determined by secondary ion mass spectrometry (SIMS), remained stable in the low 10¹⁵ cm⁻³ range, enabling semi-insulating or precisely doped crystal growth. Purity and reproducibility were verified by a cross-technique analytical approach including glow discharge mass spectrometry (GDMS), and inductively coupled plasma mass spectrometry (ICP-MS). Microstructural investigations confirmed dense, void-free grains and high crystallographic uniformity. With production capacity scaling toward 60 tons per month, this CVD-based SiC source material establishes a robust platform for next-generation PVT growth. Its combination of ultra-low contamination, structural integrity, and scalable manufacturing positions it as a key enabler for optical SiC applications such as transparent wafers for augmented reality (AR) systems, as well as advanced power and RF devices.

Abstract: Thick epitaxy with different buffer and drift layer growth rates are studied. Epilayer with higher growth rates demonstrates lower basal plane dislocaiton (BPD) but higher stacking faults. We use the optimum growth rate found from the aforesaid experiments to achieve 100um and 200um epilayers. BPD pile up was observed, especifally at the edges of the epilayer rendering an exclusion area upto 15mm from the edge. Hence, we argue that it is essential to consider higher exclusion region for thicker epilayers. Large, pits and bumps are observed for thicker epitaxy, upto a diameter of 48µm for 200µm epilayers. Finally, we polish the epilayers and demonstrated 98% and 95% total usable area (TUA) for 100µm and 200µm epitalayers respectively.

Abstract: In the solution growth method for silicon carbide (SiC) single-crystal fabrication, in-situ observations were performed inside the furnace to monitor the meniscus at the seed–solution interface. A meniscus formed at the contact between the seed crystal and the solution, and variations in the reflections on the solution surface enabled optical monitoring and control of this interface. The observed surface images were also dependent on the frequency of the induction heating. Computational fluid dynamics (CFD) simulations indicated that lowering the heating frequency causes an upward displacement of the solution surface at its central region, producing a locally elevated contact position between the seed crystal and the solution. These findings demonstrate that in-situ observation constitutes an effective approach for precise control of meniscus shape during solution growth of SiC single crystals.

Abstract: Close Space PVT (CS-PVT) is a modification of standard PVT exhibiting a short source-to-seed-distance and enabling a large variety of growth process variations to meet the specific requirements of the SiC material (i.e. special polytype and/or doping) to be grown. In this work, we study the growth of 4H-SiC p-i-n structures exhibiting thick SiC layers to be used as SiC photovoltaic cells for remote power transfer in space. Nevertheless, the found results are also applicable (i) to the SiC thick layer growth of power electronic devices and (ii) SiC pucks with a thickness of up to 10mm. In addition, we present the new type of growth machine TableTopCS^TM in its design being dedicated for the special crucible configuration of CS-PVT.

Abstract: We have investigated the applicability of a new type of 3C-SiC powder source material during PVT growth which consist of a particle size of ca. 10 µm (aggregates up to ca. 150 µm). In-situ X-ray visualization of 75 mm and 100 mm PVT growth runs showed a smooth SiC powder consumption during growth. Using Raman spectroscopy, we have found a high 4H-SiC polytype stability and a low residual stress distribution in the intentionally n-type doped grown crystals.