Abstract

Recently the spectroscopic measurements of the second harmonic generation (SHG) response of buried Si-SiO₂ interfaces have been presented in a number of papers |1|. however, the whole detected SHG signal was supposed to be attributed with the response of the stressed subsurface layer. Here we have demonstrated that two additional bulk contributions in the SHG intensity neglected in previous spectroscopic measurements should be necessarily taken into consideration, namely the dipole electric-field-induced SHG produced in the space charge region near the Si surface due to initial band banding and the quadrupole SHG. In the current work we have extracted the spectra of these three contributions from the azimuthal dependences for biased Si(001)-SiO₂ interface in the metal-oxide-scmiconductor structure through isotropic character of surface and bulk electric-field-induced SHG (EISH) contributions and the presense of the anisotropic part in the bulk quadrupole term. The spectra of both bulk contributions ${\chi }_{\text{aniso }}^{(2),BQ}$ and χ⁽³⁾, ^BD present resonance peaks centered at 3.38 eV close to the E₁ critical point of silicon, whereas the surface contribution χ^(2),S spectra presents the redshifted peak near 3.29 eV (Fig. 1). The phenomenological model that took into account the spatial distribution of the dc-electric-field inside the space charge region within Fermi-Dirac statistics as well as the retardation of the EISH wave was used to extract the EISH contribution. Finally, the SHG spectroscopy on biased Si-SiO₂ interface demonstrates the importance of the account of bulk contributions in the SHG and confirms the differences in spectra of surface and bulk contributions.

© 1996 IEEE