Many-body effects in the first excited subband of the n-inversion layer of Si

We have calculated the self-energies of electrons in the lowest and first excited sub-bands of Si inversion layers. The self-consistent wavefunctions calculated in the Hartree approximation were used, and dynamic screening was approximated by the Lundqvist-Overhauser model. The correlation energy of an electron in the excited band is quite large: about -10 meV at an inversion layer density of 1011 cm-2 to about -16 meV at 3 × 1012 cm-2. The calculated separation between subbands is in very good agreement with available experimental measurements. An exciton is predicted with a binding energy of 0.9 meV at Ninv = 1012 cm-2 calculated in the static approximation. © 1976.