Electric field induced second harmonic generation spectroscopy on a metal-oxide-silicon structure

Spectroscopic electric-field-induced second harmonic generation on a Si(111)–SiO2–Cr metal-oxide-silicon structure shows a bias-independent ‘‘interface’’ resonance at 3.25 eV and a ‘‘bulk’’ resonance at 3.43 eV which is strongly bias dependent. The symmetry forbidden bulk dipole contribution becomes observable, and even dominating, due to the bias-induced band-bending that breaks the bulk inversion symmetry. The origin of these resonances is discussed, as well as the prospects for using second harmonic generation as a probe of metal-oxide-silicon characteristics.