Femtosecond laser diagnostics of the built-in electric field across the p+-Si/SiO2 interface and its ultrafast shielding

Abstract

Ultrafast shielding of the built-in electric field E0 across the p+-Si/SiO2 interface of boron doped Si upon near infrared femtosecond (fs) laser pulse irradiation (73 ± 5 fs, 35 GW/cm 2≤ Ipeak (ω) ≤ 115 GW/cm2) is shown to be dominated by electron-hole (e-h) pairs generated via two-photon absorption (TPA), whereas contributions from one-photon absorption (OPA) appear negligible. E0 shows up in the instantaneous signal I (2 ω) (t ≈ 0) ≈ I (2ω) (E0) of the Electric Field Induced Second Harmonic (EFISH). Its power law is derived from the linear log I (2ω) (E0) vs. log ( peak (ω)n plots of six fs laser wavelengths 741.2 nm ≤ λ ≤ 801.0 nm for the first time. These reveal 1.2 ≤ n(λ) ≤ 2.1 with the minimum at λ = 752.4 nm (2hν = 3.3 eV) related to resonantly enhanced TPA. Shielding of E0 by e-h pairs from OPA cannot be detected by EFISH in the same fs laser pulse as their generation requires relatively slow electron-phonon coupling. © 2013 AIP Publishing LLC.