Large band gap bowing of MBE-grown GeC/Si(001) layers

The band structure of GeC epilayers on Si(0 0 1) substrates has been investigated by Fourier transformation infrared spectroscopy, photoreflectance and spectroscopic ellipsometry measurements. The Ge 1− x C x epilayers were grown by molecular beam epitaxy with the substitutional C content x from 0 to 0.025. The absorption coefficient α of these epilayers obeyed a square-root law for the photon energy hν , indicating an indirect band gap semiconductor. The fundamental band gap energy E g and the interband transition-energy E 0 remarkably decreased with increasing x . Large band gap bowing was found out in the GeC epilayers and large bowing parameter of 13.1 eV was evaluated. The modification of the band structure by the incorporation of C atoms was occurred.