Band structure properties, phonons, and exciton fine structure in 4H-SiC measured by wavelength-modulated absorption and low-temperature photoluminescence

Owing to its hexagonal symmetry, indirect band gap, and relatively large unit cell, the electronic band structure of 4H-SiC is comprised of a complicated series of anisotropic valence and conduction band extrema even very near to the uppermost valence band maximum and lowest conduction band minimum. This has presented a difficult challenge to those experiments which have attempted to resolve the small energy separations between these band extrema. To overcome this challenge, we have measured the wavelength-modulated absorption (WMA) spectrum of 4H-SiC over a broader wavelength range (3500–3800 Å) and at a higher resolution (