Investigation of energy levels of Er-impurity centers in Si by the method of ballistic electron emission spectroscopy

Abstract

The method of ballistic electron emission spectroscopy is used for the first time to study the energy spectrum of Er-impurity complexes in Si. The features are observed in the ballistic electron spectra of mesa diodes based on p+-n+ Si structures with a thin (∼30 nm) p+-Si:Er surface layer in the region of ballistic-electron energies eVt lower than the conduction-band-edge energy Ec in this layer. They are associated with the tunnel injection of ballistic electrons from the probe of the scanning tunnel microscope to the deep donor levels of the Er-impurity complexes in the p+-Si:Er layer with subsequent thermal excitation into the conduction band and the diffusion to the p+-n+ junction and the direct tunneling in it. To verify this assumption, the ballistic-electron transport was simulated in the system of the Pt probe, native-oxide layer SiO2-p+-Si:Er-n+, and Si substrate. By approximating the experimental ballistic-electron spectra with the modeling spectra, the ground-state energy of the Er complex in Si was determined: Ed ≈ Ec − 0.27 eV. The indicated value is consistent with the data published previously and obtained from the measurements of the temperature dependence of the free-carrier concentration in Si:Er layers.