Direct determination of impact ionization quantum yield in Si by ballistic-electron-emission microscopy

Ballistic-electron-emission spectroscopy on Si(111)-(7×7) patches in pinholes of thin NiSi2 films on n-type Si(111) reveals collector currents as high as 210% of the tunneling current at a tip bias of 10 V. This electron multiplication is assigned to impact ionization in Si. Its quantum yield up to 7 eV kinetic energy is extracted from the spectra and compared to recent thoeretical results. © 1994 The American Physical Society.