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.
