Optically detected cyclotron resonance investigations on 4H and 6H SiC: Band-structure and transport properties

We present experimental data on the band-structure and high-mobility transp ort properties of 6H and 4H-SiC epitaxial films based on optically detected cyclotron resonance investigations. From the orientational dependence of t he electron effective mass in 6H-SiC we obtain direct evidence for the came ls back nature of the conduction band between the M and L points. The broad ening of the resonance signal in 4H-SIC as a function of temperature is use d to extract information on electron mobilities and to conclude on the role of the different scattering mechanisms. Under high microwave powers an enh ancement of the electron effective mass is found which is explained by a co upling of the electrons with longitudinal optical phonons.