Thickness determination of 4H-SiC epitaxial films by infrared reflectance

The refractive index of n-type 4H-SiC as a function of the wave number is calculated. The results show that the epi-films with doping ranges lower than 10¹⁸ cm^-3 are the necessary condition of appearing interference fringes in the infrared reflectance spectra of SiC homoepitaxial films. A modified method is proposed based on the refractive index model varying with frequency which is more accurate and stable than the original method in a wide spectra range.