TUNNELING CURRENT SPECTROSCOPY OF ELECTRON SUBBANDS IN N-TYPE DELTA-DOPED SILICON STRUCTURES GROWN BY MOLECULAR-BEAM EPITAXY

Tunneling current measurements on n-type δ-doped Si(100) structures were carried out, with sheet doping concentrations ranging from ∼4×1012 to 2.0×1013 cm-2 at 4 K. All samples have been grown by using a low-energy ion source for antimony doping in a silicon molecular beam epitaxy system. From analysis of dI/dVg and (dI/dVg)/ (I/V g) spectra, tunneling associated with quantized electron subbands is identified. The subband energy positions relative to the equilibrium Fermi level EF0 under zero bias were determined from the tunneling current measurements as a function of the sheet doping concentration. Self-consistent theoretical calculations of the electronic structure of δ layers have been performed, and good agreement between theory and experiment is obtained for most structures in the tunneling spectra.