Abstract

Much recent second harmonic (SH) spectroscopy of the buried Si/SiO₂ interface^1,2 has been performed without deconvolving the true dipole-allowed strained-interface contribution (~10 Ä depth) from two comparable, competing bulk contributions: 1) electric-field-induced SHG from the space charge region (-100 Ä depth) and 2) bulk quadmpole SHG from the SH escape depth (-1000 Ä). Consequently, important interface spectral features such as the strain-induced redshift of the Ei critical point^1,2 could be observed qualitatively but not fully quantified. In the current work we have fully separated these three contributions and their corresponding spectra for the first time, to our knowledge, by performing electromodulated SH spectroscopy on a Si(001) metal-oxide-semiconductor (MOS) structure. The relatively simple tensorial decomposition of nonlinear electroreflectance (HER) at Si(001) interfaces permits full separation of the three contributions through their contrasting dependence on applied bias and sample azimuthal orientation.

© 1996 Optical Society of America