Surface photovoltage (SPV) transient provides a non-destructive, contact-free method for characterization of
semiconductor surfaces. Here we study SPV-transients of differently cleaned, heavily doped epiready GaAs wafers.
After a rapid initial part the transient shows a very slow decay taking place in 100 - 1000 s time scale. Chemical
NH4OH:H2O2:H2O cleaning and atomic hydrogen UHV cleaning are applied. SPV-transients are measured by Kelvin probe in normal atmospheric conditions. A large signal surface trapping model is developed which includes both
majority and minority carrier processes and covers the whole light on, steady state, light off sequence. Model fitting
allows band bending, energy and density of surface states as well as electron and hole capture cross-sections to be
extracted. The results show that the traps are electronic states in thin oxide layer covering the samples. This conclusion is
based on the finding that the capture cross-sections are very small, in the range 10-19 - 10-26 cm2, which calls tunneling for explanation. This indicates that after cleaning the oxide layer is rapidly re-grown in laboratory atmosphere in less than 30 min. Typical band bendings are 0.6 - 0.8 eV, trap energies are slightly above the mid-gap and the density of
occupied trap states is around 5×1012 cm-2 at thermal equilibrium.
The Si/SiO2 superlattices were prepared by a molecular beam deposition method, high temperature furnace annealing (1100 °C), and back-side Si wafer etching in tetramethyl ammonium solution. Transmission electron microscopy and Raman spectroscopy show that the layered structure is not preserved during high temperature treatment. The etching of the substrate increases photoluminescence of the Si/SiO2 material. Optical waveguiding was realized for the free-standing sample demonstrating its reasonable optical quality and providing the optical parameters.
Room temperature (RT) electroluminescence (EL) was obtained for the first time from Mn enriched Si/SiO2 structure. Si+ or Ar+ stimulated knock-on implantation through 20 nm Mn film with the subsequent annealing was used for EL device fabrication. Devices exhibit bright emission band at the 2.06 eV. The position does neither depend on implanted ion dose nor annealing procedure. EL is visible by naked eye even at current density as low as 1.5x10-6 Acm-2. Continuous wave external quantum efficiency 1.1x10-3 and power efficiency 1.5x10-5 have been achieved.