Aug 27, 2019

Electrical and Control Engineering, International Conference on


In this paper, with the purpose of improvement of power devices properties, the floating-junction technology was used in the 4H-SiC Schottky barrier diodes (SBD) and some parameters were optimized by software simulation. And compared with the conventional power SBDs, the electrical properties of floating-junction Schottky barrier diodes, especially the reverse blocking properties were enhanced. The breakdown voltage and specific on-resistance could reach 4.5KV and 6.15 mΩ.cm2 respectively, while in company with the increasing of Baliga figure of material (BFOM). Then we also investigated the devices switching process and temperature characteristics under definite conditions.

Source:IOPscience
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Aug 21, 2019

Surface preparation for Schottky metal - 4H-SiC contacts formed on plasma-etched SiC

Silicon-carbide-based devices frequently require a Schottky gate to be deposited on a plasma-etched surface. This paper considers the effectiveness of nine different pre-metallization surface preparation procedures in removing the etch damage. The surfaces were assessed by x-ray photoelectron spectroscopy and by current-voltage measurement of nickel Schottky diodes formed on both reactive-ion-etched and non-reactive-ion-etched silicon face 4H-SiC. The treatments included simple UV-ozone and solvent cleans, oxygen plasma, deposited oxide and thermal oxidation. It was confirmed that the only process which removed all traces of surface contamination and etch damage, producing ideal Schottky diodes, was sacrificial oxidation.





Source:IOPscience
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Aug 16, 2019

Improved ohmic contact to the n-type 4H-SiC semiconductor using cobalt silicides

Multilayer structures of cobalt and silicon have been deposited as an ohmic contact on n-type 4H-SiC substrates in order to obtain lower contact resistance and higher thermal stability. The metal structures were prepared by using electron beam evaporation on top of the silicon face of the 4H-SiC substrates, and were annealed in an atmosphere of argon with 10% hydrogen. The metal film thickness was monitored during the film deposition, and the ratio of the cobalt and silicon was fixed at 0.5 for the formation of the silicon-rich silicide structure (CoSi2). The electrical property of the ohmic contact has been significantly improved by the reduction of the oxide content in the metal contact layer. A two-step annealing process was employed to reduce oxidation problems that may occur in the heat treatment at high temperatures. The specific contact resistance of the contact structure prepared by the two-step annealing process was measured to decrease by more than one order of magnitude compared to that prepared by one-step annealing. The best result has been obtained as 1.8 × 10−6 Ω cm2 for Co/Si/Co/Si/Co metal structures after two-step annealing, at 500 °C for 600 s and 800 °C for 120 s. In the field emission scanning electron microscopy, the interface of the contact structure and SiC substrate was observed to have smooth surface morphology with CoSi2 grains.


Source:IOPscience
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Aug 9, 2019

Defect characterization of 4H-SiC wafers for power electronic device applications

Silicon carbide is a semiconductor of choice for the fabrication of high-power, high-temperature and high-frequency electronic devices.

Nevertheless, such a material still presents many problems as regards the crystallographic quality and the presence of defects, which influence the device performance.

We have investigated 4H-SiC wafers and 4H-SiC epitaxial layers by microscopy and structural techniques in order to obtain information about the defect morphology. The goal of this analysis will be to correlate them with the electrical properties of SiC for power electronic device applications.




Source:IOPscience
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Aug 1, 2019

Experimental investigation of slow-positron emission from 4H-SiC and 6H-SiC surfaces

Slow-positron emission from the surfaces of as-grown n-type 4H-SiC and 6H-SiC (silicon carbide) with a conversion efficiency of ~ 10−4 has been observed. After 30 min of 1000 oC annealing in forming gas, the conversion efficiency of the n-type 6H-SiC sample was observed to be enhanced by 75% to 1.9 × 10−4, but it then dropped to ~ 10−5 upon a further 30 min annealing at 1400 oC. The positron work function of the n-type 6H-SiC was found to increase by 29% upon 1000 oC annealing. For both p-type 4H-SiC and p-type 6H-SiC materials, the conversion efficiency was of the order of ~ 10−5, some ten times lower than that for the n-type materials. This was attributed to the band bending at the p-type material surface which caused positrons to drift away from the positron emitting surface.


Source:IOPscience
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