THz emission from argon implanted silicon surfaces

THz emission from semiconductor surfaces is influenced by the sign and strength of the surface field as well as the relaxation dynamics of the photoinduced carriers. In this paper, an experimental study on argon implanted silicon surfaces is presented. Moderately doped silicon wafers were implanted with 100 keV argon ions with fluences ranging from 1011 to 5×1014cm−2. The THz emission from silicon is strongly enhanced after ion implantation, while the actual THz amplitude depends on the ion dose. For small fluences the increase of the THz amplitude is dedicated to Fermi level pinning due to the introduction of midgap states. In case of highly damaged surfaces where ellipsometry confirms the formation of amorphous zones the THz amplitude starts to decrease. The results demonstrate that for small damage levels THz emission is mainly sensitive to the changed electronic properties whereas for highly damaged surfaces it mostly reacts on the altered generation profile that stems from the changed optical properties of a damaged surface region.