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  • Author: M. Guziewicz x
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R. Kisiel, M. Guziewicz, K. Golaszewska, M. Sochacki and W. Paszkowicz

Abstract

A mechanism of carriers transport through metal-semiconductor interface created by nickel or titanium-based ohmic contacts on Si-face n-type 4H-SiC is presented herein. The mechanism was observed within the temperature range of 20 °C ÷ 300 °C which are typical for devices operating at high current density and at poor cooling conditions. It was found that carriers transport depends strongly on concentration of dopants in the epitaxial layer. The carriers transport has thermionic emission nature for low dopant concentration of 5×1016 cm−3. The thermionic emission was identified for moderate dopant concentration of 5×1017 cm−3 at temperatures higher than 200 °C. Below 200 °C, the field emission dominates (for the same doping level of 5×1017 cm−3). High dopant concentration of 5×1018 cm−3 leads to almost pure field emission transport within the whole investigated temperature range.

Open access

A. Taube, M. Guziewicz, K. Kosiel, K. Gołaszewska-Malec, K. Król, R. Kruszka, E. Kamińska and A. Piotrowska

Abstract

The paper presents the results of characterization of MOS structures with aluminum oxide layer deposited by ALD method on silicon carbide substrates. The effect of the application of thin SiO2 buffer layer on the electrical properties of the MOS structures with Al2O3 layer has been examined. Critical electric field values at the level of 7.5–8 MV/cm were obtained. The use of 5 nm thick SiO2 buffer layer caused a decrease in the leakage current of the gate by more than two decade of magnitude. Evaluated density of trap states near the conduction band of silicon carbide in Al2O3/4H-SiC MOS is about of 1×1013 eV−1cm−2. In contrast, the density of the trap states in the Al2O3/SiO2/4H-SiC structure is lower about of one decade of magnitude i.e. 1×1012 eV−1cm−2. A remarkable change in the MOS structure is also a decrease of density of electron traps located deeply in the 4H-SiC conduction band below detection limit due to using of the SiO2 buffer layer.