Spatially Resolved Raman Spectroscopy Studies of Damage Formation in 4H-SiC Induced by Proton Irradiation

Abstract

Silicon carbide (SiC) is a material of choice for high-power, high-frequency and high-temperature electronics applications, owing to its high thermal conductivity, its high electric field breakdown strength and its wide energy band-gap. However, the potential of SiC can only be realized if a good understanding of the different processing steps for device fabrication is achieved. One such step is ion irradiation, a crucial process for materials doping. However, ion irradiation also produces damage and defects that can deteriorate the properties of the material. In this work, we have used spatially resolved visible Raman spectroscopy to understand damage formation upon irradiation of single crystal 4H-SiC. The irradiation was performed using 3 MeV protons at doses of 1.0, 2.5, 5.0, and 10 (×10^13 proton/cm^2) and its effect on the corresponding Raman signals, and in particular, the Transverse Optical (TO) modes, was investigated. The Raman analysis as a function of laser beam location on the samples allowed to unambiguously delimit the damaged areas on the samples surface. Damage formation was found to increase with increasing irradiation doses and induces changes in the intensity, lineshape and shift of the Raman peak. The evolution of the Raman intensity with irradiation indicate an accumulation of isolated point defects, and for low doses, these changes could be explained by partial recrystallization of the SiC structure. The damaged zones in the samples also show the existence of stresses in the material as deduced from the observed changes in the Raman peak positions. These results were also correlated to the thermal properties measured on the samples and provide greater understanding of the effect of damage on the bonding and physical properties of SiC.