Kyoto University · Engineering
Professor Keita Tachiki's research lab specializes in wide-bandgap semiconductor devices, with a primary focus on 4H-SiC (silicon carbide) metal-oxide-semiconductor field-effect transistors (MOSFETs) and MOS capacitors. The lab investigates fundamental interface engineering between SiC and SiO₂, emphasizing defect passivation techniques such as H₂ etching, N₂/NO annealing, and oxidation-minimizing processes to achieve low interface state densities and high channel mobility. Their work addresses critical challenges in power electronics, including short-channel effects, threshold voltage stability, and the compatibility of normally-off operation with high performance in SiC-based power devices.
Figures are computed from collected data and may differ slightly.
Abstract 4H-SiC(0001) metal-oxide-semiconductor field-effect transistors (MOSFETs) and MOS capacitors were fabricated by the following procedures: H 2 etching, SiO 2 deposition, and nitridation, and their electrical characteristics were evaluated. Substantially low interface state densities (4–6 × 10 10 cm −2 eV −1 ) and high channel mobilities (80–85 cm 2 V −1 s −1 ) were achieved by N 2 annealing or NO annealing after H 2 etching and SiO 2 deposition. The threshold voltage of the MOSFETs fabri
In this brief, the minimum channel length (the channel length at which short-channel effects (SCEs) begin to occur) in SiC MOSFETs was experimentally determined. We fabricated 4H-SiC MOSFETs with various channel lengths and acceptor concentrations and analyzed their electrical characteristics. We propose a method for determining the minimum channel length in silicon carbide (SiC) MOSFETs, focusing on the increased rate of the drain current in the saturation region, and define the minimum channel
Abstract We formed SiC/SiO 2 structures by various procedures that excluded an oxidation process. We found that a SiC/SiO 2 interface with a low interface state density near the conduction band edge of SiC ( D it ∼ 4 × 10 10 cm −2 eV −1 at E c −0.2 eV) is obtained for a fabrication process consisting of H 2 etching of the SiC surface, SiO 2 deposition, and high-temperature N 2 annealing. D it is rather high without H 2 etching, indicating that etching before SiO 2 deposition plays a significant
Effects of high-temperature (1400 °C–1600 °C) N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> annealing on the interface states of 4H- SiC/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the channel mobility of 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) were investigated. It is demonstrated that high-temperature N <sub xmlns:mml="http://www.w3.org/1998/
In this brief, the influence of high-density traps at the SiO2/SiC interface on short-channel effects was investigated, and a model describing channel length dependence of the threshold voltage (i.e., the gate voltage at a given drain current) is proposed. First, we determined the densities of interface states and fixed charge in 4H-SiC n-channel MOSFET by fitting the calculated gate characteristics to the experimental data, and acquired the density of trapped electrons from the obtained results
Abstract The effects of a process that minimizes oxidation of SiC on the channel mobility of heavily doped 4H-SiC (0001), (112̄0) and (11̄00) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated. High field-effect mobilities were obtained for these MOSFETs even when the acceptor concentration of the p-body ( N A ) exceeded 1 × 10 18 cm −3 . The field-effect mobility for the (0001) MOSFETs reached 25 cm 2 V −1 s −1 ( N A = 1 × 10 18 cm −3 ). The fabricated (11 <mml:math
Abstract In this study, using first-principles calculations, we investigate the behavior of electrons at the SiC/SiO 2 interface when nitrogen is introduced as a dopant within a few nm of the SiC surface. When a highly doped nitrogen layer (5 × 10 19 cm −3 ) is introduced within a few nm of the SiC(112̅0) surface, the electronic state is not significantly affected if the doping region is less than 4 nm. However, if the doping region exceeds 4 nm, the effect of quantum confinement decreases, whic
In this study, using first-principles calculations, we investigate the behavior of electrons at the SiC/SiO$_2$ interface when nitrogen is introduced as a dopant within a few nm of the SiC surface. When a highly doped nitrogen layer (5$\times$10$^{19}$ cm$^{-3}$) is introduced within a few nm of the SiC(11$\bar{2}$0) surface, the electronic state is not significantly affected if the doping region is less than 4 nm. However, if the doping region exceeds 4 nm, the effect of quantum confinement dec
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