Low-Energy Yield Spectroscopy as a Novel Technique for determining Band Offsets: Application to the c-Si(100)/a-Si:H Heteroestructure

We present a new experimental method for determining band lineups at the semiconductor heterojunctions and apply it to the c−Si(100)/a−Si:H heterostructure. This method uses a modern version of an old spectroscopy: the photoelectric yield spectroscopy excited with photons in the near UV range. It is shown that both substrate and overlayer valence-band tops can be identified in the yield spectrum due to the high escape depth and the high dynamical range of the technique, thus allowing a direct and precise determination of the band lineup. A value of ΔEV=0.44±0.02eV was found for the valence band discontinuity.