Angle-resolved photoelectron spectroscopy study of initial stage of thermal oxidation on 4H-SiC(0001)

A key to improving the performance of SiC MOSFETs is to clarifythe SiO2/SiC interface structure formed by thermaloxidation. We have investigated the initial stage of thermal oxidation on 4H-SiC(0001) by angle-resolved photoelectron spectroscopy. From the changes inthe Si 2p3/2 and C 1s photoelectron spectra, the changes in the chemical bonding state of the SiO2/SiC structure with the progress of thermal oxidation were observed. We also found that the intensity of C–O bonds in the case of 4H-SiC(0001) was smaller thanthat in the case of 4H-SiC withthe same oxide thickness and that the oxidation rate of 4H-SiC(0001) is already slower than that of 4H-SiC in the early stage of oxidation.


Source:IOPscience
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Ultra high voltage MOS controlled 4H-SiC power switching devices

Ultra high voltage (UHV, >15 kV) 4H-silicon carbide (SiC) power devices have the potential to significantly improve the system performance, reliability, and cost of energy conversion systems by providing reduced part count, simplified circuit topology, and reduced switching losses. In this paper, we compare the two MOS based UHV 4H-SiC power switching devices; 15 kV 4H-SiC MOSFETs and 15 kV 4H-SiC n-IGBTs. The 15 kV 4H-SiC MOSFET shows a specific on-resistance of 204 mΩ cm2 at 25 °C, which increased to 570 mΩ cm2 at 150 °C. The 15 kV 4H-SiC MOSFET provides low, temperature-independent, switching losses which makes the device more attractive for applications that require higher switching frequencies. The 15 kV 4H-SiC n-IGBT shows a significantly lower forward voltage drop (VF), along with reasonable switching performance, which make it a very attractive device for high voltage applications with lower switching frequency requirements. An electrothermal analysis showed that the 15 kV 4H-SiC n-IGBT outperforms the 15 kV 4H-SiC MOSFET for applications with switching frequencies of less than 5 kHz. It was also shown that the use of a carrier storage layer (CSL) can significantly improve the conduction performance of the 15 kV 4H-SiC n-IGBTs.



Source:IOPscience
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Silicon carbide of Ni/6H-SiC and Ti/4H-SiC type Schottky diode current-voltage characteristics modelling

On the base of the physical analytical models based on Poisson's equation, drift–diffusion and continuity equations the forward current–voltage characteristics of 6H-SiC and 4H-SiC type Schottky diode with Ni and Ti Schottky contact have been simulated. It is shown on the base of analysis of current–voltage characteristics in terms of classical thermionic emission theory it is shown that the proposed simulation model of Schottky diode corresponds to the almost "ideal" diode with ideality factor n equals 1.1. Because of this it is determined that the effective Schottky barrier height B equals 1.57 eV and 1.17 eV for Ni/6H and Ti or 4H silicon carbide Schottky diode type, respectively.



Source:IOPscience
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Ti/4H-SiC Schottky diode breakdown voltage with different thickness of 4H-SiC epitaxial layer

Breakdown voltage for Ti/4H-SiC type Schottky diode with six guard rings have been calculated theoretically and by mean of numerical simulations. It is shown that the breakdown voltage can be increase at the minimum on 100 V in case when thickness of the n-type 4H-SiC epitaxial layer increase from 18 up to 22 μm. It is established that the breakdown voltage value for Ti/4H-SiC type Schottky diode with guard rings calculated by mean simulation in ATLAS program and theoretically have good approximation. Thus, above approach gives the possibility for projection of diode structure with different 4H-SiC epitaxial layer thickness with higher breakdown voltage value.

Source:IOPscience

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