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As a wide bandgap and single crystalline semiconductor, 4H-polytype silicon carbide (4H-SiC) is an excellent material choice for devices operating in harsh environments of high temperature, high pressure, radiation, chemical and biomedical, etc. In this letter, an electrostatically actuated 4H-SiC microresonator was fabricated by dopant-selective photoelectrochemical etching of n-p-n homoepitaxial structure. Resonant frequencies of 3.463 MHz (out-of-plane) and 16.9 MHz (in-plane) were attained and they are in good agreement with theoretical calculation. To the best of our knowledge, these frequencies are the highest values ever reported from single crystalline 4H-SiC MEMS resonators. [ABSTRACT FROM PUBLISHER]

In this letter, a counter-doped junction termination extension (CD-JTE) structure was experimentally implemented and studied. Two groups of 4H-SiC PiN diodes were fabricated with two n-type drift layer thicknesses of 11 and 30 \mu \textm , respectively, and with different termination structures, in order to demonstrate the wide JTE dose tolerance of CD-JTE. Three different doses, 1.7 \times 10^13 , 2.2\times 10^13 , and 2.8\times 10^13 cm ^-2 , were used for the critical JTE implantation. The measured breakdown voltages (BVs) of the diodes with all termination structures and JTE doses were compared with simulation predictions. Electroluminescence at the BV was recorded and used to locate the peak electrical field. The test results matched well with the simulation results. As a result of the effectiveness and robustness of the CD-JTE, the best achieved BVs from the diodes on the 11- and 30- \mu \textm epilayers were 1850 and 4800 V, respectively. [ABSTRACT FROM AUTHOR]

This research proposes a novel 4H-SiC power device structure—different concentration floating superjunction MOSFET (DC-FSJ MOSFET). Through simulation via Synopsys Technology Computer Aided Design (TCAD) software, compared with the structural and static characteristics of the traditional vertical MOSFET, DC-FSJ MOSFET has a higher breakdown voltage (BV) and lower forward specific on-resistance (Ron,sp). The DC-FSJ MOSFET is formed by multiple epitaxial technology to create a floating P-type structure in the epitaxial layer. Then, a current spreading layer (CSL) is added to reduce the Ron,sp. The floating P-type structure depth, epitaxial layer concentration and thickness are optimized in this research. This structure can not only achieve a breakdown voltage over 3300 V, but also reduce Ron,sp. Under the same conditions, the Baliga Figure of Merit (BFOM) of DC-FSJ MOSFET increases by 27% compared with the traditional vertical MOSFET. Ron,sp is 25% less than that of the traditional vertical MOSFET. [ABSTRACT FROM AUTHOR]

High-voltage 4H-SiC lateral MOSFETs with different gate layouts, channel lengths, and drift region lengths were fabricated on the (0001) face of a high-purity semi-insulating substrate. A breakdown voltage of 3520 V was achieved on a circular gate device with a channel length of 5 \mu\m and a drift region length of 80 \mu\m. This is, to the best knowledge of the authors, the highest value among 4H-SiC lateral MOSFETs ever reported. The specific on-resistance is 600 \m\Omega\-cm^2, which results in a figure-of-merit (\BV^2/Ron, sp) of 20.6 \MW/cm^2, which is comparable with other 4H-SiC lateral MOSFETs reported in the literature. It was found that the use of a circular gate layout effectively reduces the reverse leakage current at high voltages. [ABSTRACT FROM PUBLISHER]

Abstract: The goal of this research is to investigate the correlation of reverse characteristics of Schottky barrier diodes (SBDs) and surface morphological defects on 4° (off-axis) carbon (C) face, 4° and 8° silicon (Si) face 4H-SiC. Different dimensions of SBDs with boron-implanted edge terminations are fabricated on 4° C-face, 4° and 8° Si-face 4H-SiC samples. The ideality factor for these three samples is about 1.1. Average breakdown voltages of 4° Si-face 4H-SiC SBDs are higher than the other two samples, particularly for large size SBDs. Breakdown voltages of 1500 and 2000μm 4° Si-face SBDs can reach over 1000V. This value is about two times higher than the other two samples, though the root-mean-square (RMS) roughness of 4° Si-face samples obtained from atomic force microscopy (AFM) is 3.5nm. The yield of 1500 and 2000μm 4° Si-face 4H-SiC SBDs with a breakdown voltage over 1000V is more than 50%, much higher than the other two samples. [Copyright &y& Elsevier]

Silicon carbide (SiC), a wide bandgap semiconductor, is more desirable over conventional silicon (Si) to satisfy the increasing demands for microelectromechanical system (MEMS) to operate in harsh environments due to the excellent physical, mechanical and chemical inertness. Research in MEMS devices based on single or polycrystalline SiC on Si or SOI substrate, such as 3C-SiC polytype, have been widely carried out. Another promising candidate is “all”-SiC, i.e., homoepitaxial single crystal SiC layer on single-crystal SiC substrate, such as 4H and 6H-SiC polytypes. They truly exploit the superior material properties of SiC and provide advantages for MEMS devices to operate in hostile conditions. In this work, 4H-SiC MEMS actuators in cantilever and bridge configurations were fabricated by a surface micromachining process, and their dynamic responses were characterized to determine Young’s modulus of 4H-SiC and frequency performance. Resonant frequencies of 1.208 MHz from cantilever and 1.338 MHz from bridge actuators were achieved. These high frequency operation capabilities are particular interesting for ultrafast and high resolution sensors and actuators. [ABSTRACT FROM AUTHOR]

Abstract: SiO2 encapsulation layer was studied for aluminum (Al) and phosphorus (P) implant activation anneal in 4H-SiC. Both Al- and P+ implantation were carried out at 650°C followed by activation anneal at 1400°C to 1500°C. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and four-point-probe (FPP) measurements were performed to examine surface stoichiometry, roughness, and sheet resistance of the implanted SiC regions. The effect of using SiO2 encapsulation layer for Al implant activation on the performance of 4H-SiC p-i-n diodes with both p-type active region and JTE region formed by Al implantation was also investigated. Forward and reverse characteristics including saturation current density J 0 , ideality factor η, reverser leakage current density J L and threshold breakdown voltage V BR have been extracted. The results show that SiO2 encapsulation effectively protects the SiC surface during high temperature implant activation for both Al- and P+. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wet oxidation at 950°C followed by NO anneal at 1175°C reduces the interface trap density to 4–6×1011 cm−2 eV−1. [•] The positive flat band voltage shift caused by low temperature wet oxidation can be suppressed by the following NO anneal. [•] The oxide breakdown fields for Al- and N-implanted C-face 4H-SiC samples are about 1.5 and 5MVcm−1, respectively. [•] The oxide breakdown field of dry oxidation at 950°C is the same as that of wet oxidation at 950°C. [ABSTRACT FROM AUTHOR]