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Silicon carbide, a wide band-gap semiconductor material characterized by high-thermal conductivity, high-breakdown field and robust mechanical properties is well recognized for its potential in high-power, -temperature and -frequency electronics applications. Rectifying Schottky contact is a fundamental part of various SiC-based electronic devices including Schottky diodes, field-effect transistors and fast-switching rectifiers. Many of metals like Ai, Pt, Ni, Ti have been used to form Schottky contacts with high barrier height on n-SiC, but these metals are reactive with SiC at temperature range of 400 - 600 °C leading to degradation of the contacts. To improve thermal stability of the Schottky contacts rare earth metals are promising to be successfully employed in mentioned devices. In this approach we chose iridium and iridium oxide for metallization taking into account high work function, chemical resistance and good electrical conductivity.
Now, we report on the Ir and IrO2 Schottky contacts to 4H n-SiC. Metallization was deposited by DC/RF magnetron sputtering in Ar or in reactive O2/Ar plasma. The deposition parameters were optimized to obtain high adhesion, low film stress and conductivity of the films as high as possible. Surface morphology of the films was characterized by optical microscopy, crystal structure was examined using x-ray diffraction. The barrier height was measured by current-voltage and capacitance-voltage techniques. The influence of annealing temperature and atmosphere on the metallic film and contact properties has been examined. The contact structures were thermally treated up to 900°C in RTP processes or aged in 600°C up to 100h in various ambient (Ar, O2, Air). The annealing at intermediate temperature slightly reduces resistivity and stress of the IrO2 film. The Schottky barrier heights of the as-deposited Ir and IrO2 on n-SiC are 1.40 eV and 1.53 eV, respectively. Annealing at 600°C for 10 min. increases slightly the barrier height but the subsequent annealing up to 100 h does not influence on that barrier height. The stability of the contacts at higher temperatures will be discussed.
The research is partially supported by the Ministry of Science and High Education, Poland, under the grant 3T11B 042 30.
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