Ionization of a Silicon Surface Layer Induced by a High-Intensity Subpicosecond Electric Field

The ionization of a silicon surface layer induced by an electric field with a strength of up to 17 MV/cm and a rise time of \(\approx \) $\approx$ 245 fs has been studied for the first time. The generation rate of free carriers induced by electric field has been experimentally determined. It has been shown that the average concentration of electrons in the conduction band in surface layer reaches \(\sim 3\times 10^{19}\) $\sim 3\times {10}^{19}$  cm \(^{-3}\) ${}^{-3}$ , which corresponds to the ionization rate of \(1.4\times 10^{14}\) $1.4\times {10}^{14}$  s \(^{-1}\) ${}^{-1}$ . A new method is proposed for synchronizing the THz pulse temporal profile measured by electro-optical sampling with the results of pump-probe measurements based on second harmonic generation.