RESONANT PHOTOEMISSION-STUDY ON THE BORON 1S EXCITON OF THE WIDE-BAND-GAP SEMICONDUCTOR C-BN

The B 1s exciton spectrum of the wide-band-gap semiconductor c-BN has been studied by resonant photoemission spectroscopy. The core-exciton band is found with a binding energy of about 1.2 eV. The constant-initial-state spectra for the valence-band features indicate that the B 1s exciton is the intermediate state for the resonant photoemission from the valence band. A satellite is found below the lower valence band by the resonant photoemission at B 1s exciton. The energy distribution curves of the valence band are qualitatively in agreement with the energy-band density-of-states curves but the discrepancy is conspicuous for the conduction band. The remarkable Fermi-level shift is found between p-type and n-type c-BN in accord with the rigid-band model, in spite of the large band-bending effect.