Carbonic inclusions on SiC/SiO2 interface investigated with Raman Scattering

Silicon carbide (SiC) is a wide band gap semiconductor suitable for high power and frequency electronic devices. The most important features of the material making it promising in this application are good thermal conductivity, high breakdown voltage and formation of native SiO2 layer on the surface of SiC substrate by thermal oxidation. However, the material has significant drawbacks. The most important one is low surface mobility. The surface mobility of the charge carriers is decreased by near interface states (NIT's — Near Interface Traps) — caused by defects formed in the vicinity of SiC/SiO2 interface. There are several candidates for NIT's and one of them is the occurrence of carbonic structures. Raman spectroscopy provides information about investigated structure without destruction of the sample. The aim of this work was to look for carbonic inclusions in 4H and 3C polytypes of SiC. The attention was focused on this part of the range of the Raman Shift where the strongest bands of carbonic structures are expected.

Research highlights
► Near Interface Traps (NIT's) are responsible for decrease carrier mobility.
► Raman spectroscopy can detect structures located at the interface.
► Application of two different laser lines for this purpose works efficient.
► Experimental procedure does not destroy the sample.
► Measurement of electrical parameters are possible after spectroscopic study.