Comparative Ellipsometric Analysis of Silicon Carbide Polytypes 4H, 15R, and 6H Produced by a Modified Lely Method in the Same Growth Process

Abstract

A model is suggested for a quantitative analysis of the dependence of the dielectric function of hexagonal silicon carbide polytypes on photon energy in the range of 0.7–6.5 eV. The model, which is the sum of two Tauc–Lorentz oscillators (main and minor) with a common energy gap, is used to describe three hexagonal silicon carbide polytypes (4H, 15R, 6H) obtained in the same growth process. Both C- and Si-faces of each polytype are analyzed. A number of conclusions are drawn about how the oscillator parameters depend on the degree of hexagonality of a polytype and on the type of a surface face. The strongest dependence is that the amplitude of the minor oscillator grows with increasing degree of hexagonality of a polytype. The increase in the energy gap on passing from the C-face (000 $$\bar {1}$$ ) to the Si-face (0001) is also worthy of note.