Infrared absorption spectra of 4H silicon carbide

We performed infrared absorption measurements on 4H-SiC samples with polari zation E // c and E perpendicular to c at 8, 85 and 300 K. From the strong temperature dependence of the absorption lines, electronic transitions are separated from vibronic transitions. The electronic transition lines betwee n 300 and 500 cm(-1) are assigned to the shallow nitrogen donor. It is foun d that the electronic transitions of the shallow nitrogen donor are polariz ation dependent. Zeeman spectroscopy was performed to study the influence o f the magnetic field on the electronic transitions up to 15 T. The results show no linear Zeeman splitting and only a diamagnetic shift. This is consi stent with the effective mass tenser of three different diagonal components in 4H-SiC.