Photoemission Studies of 2p Core Levels of Pure and Heavily Doped Silicon

The energy distribution curves of the 2p core levels of pure and heavily doped Si are investigated using highly monochromatized (≈︁ 0.1 eV) synchrotron radiation (105 to 140 eV). Shifts and broadenings of the spectra with doping and with the energy of the exciting photons are observed and interpreted in terms of the electrostatic band bending at the semiconductor surface and, for pure Si, of surface core shifts. The “absorption” spectrum of the 2p → conduction band transitions is studied for the same materials with the partial yield technique. By combining the absorption spectra and the core level EDC's a value of EB = (0.18 ± 0.2) eV for the core exciton binding energy is determined. Small differences in the 2p → conduction edge both with doping and with the energy of the exciting photons are observed and discussed.