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We demonstrate the usefulness of the thermally-stimulated current (TSC) technique for investigating shallow interface state defects in silicon carbide metal–oxide–semiconductor (MOS) structures. For dry oxides, low-temperature TSC measurements reveal a high density of near-interfacial oxide traps (border traps) close to the band edges of 6H–SiC. Furthermore we find that annealing the SiC/SiO2 interface in pyrogenic steam at 950 °C (reoxidation) essentially reduces the density of deep interface states, while it increases the density of shallow states. Our results agree with observations of the appearance of a negative oxide charge in reoxidized MOS capacitors and the corresponding increase of the threshold voltage in n channel metal–oxide–semiconductor field-effect transistors.

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We study the 4H-SiC/SiO 2 interface by using thermally stimulated current (TSC) measurements and find an extremely high density of shallow traps near the conduction band edge at the SiC/SiO 2 interface (> 10 13 cm −2 ). The TSC spectra reveal two distinguishable peaks and using various charging temperatures we show that the charging mechanism for the traps responsible for the high-temperature TSC peak (at about 140 K) is thermally activated. Similar TSC spectra are observed in differently prepared thermal oxides.

Abstract. Operation of n-channel MOSFET was studied at low temperatures. It has been shown that the charge state of shallow traps in the Si/SiO 2 interface is responsible for the hysteresis of transistor drain characteristics in the prekink region. Thermally activated emptying of these traps leads to the sharp decrease of the current in the subthreshold mode of transistor operation