Electronic levels in surface space charge layers on Si(100)

The energy-level spacings for electrons and holes in surface-charge layers on Si(100) are determined from a measurement of direct optical absorption of far-infrared laser radiation guided along the surface. At photon energies in the range 5.64-15.81 meV, the separation of the electric subbands is measured as a function of the surface-charge density ${N}_{s}$. For a comparison of the experimental results with theory we have characterized our metal-oxide-semiconductor system with the help of capacitance versus voltage measurements. At fixed values of ${N}_{s}$, we have examined the subband energies as a function of a substrate bias electric field. In the course of this work the influence of visible radiation on the resonance in surface-charge layers has been noted.