Tid og sted for prøveforelesning
Bedømmelseskomitè
Førsteamanuensis Marie- Laure David, University of Poitiers, France
Professor Sebastian Lourdudoss, The Royal Institute of Technology (KTH), Stockholm, Sweden
Førsteamanuensis Helge Balk, Fysisk institutt, Universitetet i Oslo
Leder av disputas
Professor Alexander Read
Veileder
- Prof. Bengt G. Svensson
- Prof. Edouard Monakhov
Summary
Fokuset i denne avhandlingen var å studere karbonvakansen i Silisiumkarbid (SiC), kjent som den mest hemmende defekten for utvikling av høy-ytelses 4H-SiC kraftelektronikk. Studien viser at karbonvakansene blir dannet ved høy temperatur. En enkel metode for å eliminere karbonvakansene gjennom varmebehandling ved moderat temperatur rundt 1400 °C-1500 °C i noen få timer under karbonrike forhold har blitt demonstrert.
The attractive physical and electronic properties of silicon carbide (SiC) make it a superior semiconductor for high power electronic devices. Several research efforts are exerted for eliminating the crystal defects which limit the material efficiency. In this thesis, the focus was on studying the carbon vacancy (VC), a missing carbon atom from its original site, which is known as the major defect in 4H-SiC severely hindering the development of high-performance power electronics. Different processes were explored to reduce the VC concentration, and near surface implantations by different ion species followed by heat processing were found to substantially eliminate the VC’s.
Technologically, fabrication of 4H-SiC electronic devices requires high temperature processing above 1800 °C, and we have investigated the formation of VC at high temperatures from 1600 to 1950 °C. However, manipulation of the thermal processing conditions by cooling down slowly after the heat treatment could suppress the VC formation, allowing for thermodynamic equilibrium of VC at lower temperatures.
A new viable and simple method for eliminating the VC based on the thermodynamic equilibrium concept was demonstrated by thermal treatments at a moderate temperature about 1400 - 1500 °C for few hours under C-rich conditions. This method can solve the problem of VC formation at high temperatures, utilizing a proposed annealing procedure of two steps. First, thermal processing at high temperature in the range of 1800-1900 °C for a few minutes to achieve activation of implanted species, and then elimination of VC can be obtained in the same annealing run by keeping the samples at 1400-1500 °C for a few hours.
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