Temperature-dependent optical absorption spectroscopy of ion irradiated silicon carbide epilayers on silicon

Transmission optical absorption spectra of ion-irradiated 3C-SiC epitaxial films on a silicon substrate are measured in the visible-near infrared range from room temperature down to about 10 K. These data show strong interference fringe patterns on top of the silicon absorption edge at about 10,460 cm¹ which limits the transmittance of the samples. The radiation damage by 2.3-MeV Si⁺ and 3.0-MeV Kr⁺ ions is studied by following the impact of ion irradiation on these transmission spectra as a function of ion fluence and at various temperatures. The temperature dependence of the optical gap of silicon is deduced from the evolution of the fundamental absorption edge and that of the refractive index of SiC is deduced from the evolution of fringe spacing. The low temperature measurements evidence the shrinkage of band gap of silicon which is assigned to the gradual amorphization of the ion-implanted zone of the substrate as a function of fluence. These new results bridge a gap in the data on the properties of ion-induced damage in silicon carbide and silicon.