Disorder effects on optical spectra and band structure of Si induced by ion implantation

Abstract

We have studied the effects of both structural and substitutional disorder in As+-implanted Si at doses from 3×1012 to 1×1016 ions cm−2 on interband optical spectra, particularly on an E1 structure at 3.4 eV. Increasing the implant dose results in a structural order-disorder transition, found to be well described by the peak-to-peak height of the E1 derivative spectra. The damage rate is defined as being based on the E1 spectral structure and is related to the fractional strength of interband optical response, in good agreement with that in effective-medium theory. The relationships between interband optical properties and electronic structure in the implanted region are discussed. After annealing, there is a red shift of the E1 threshold together with a decrease in optical response. This is attributed to substitutional impurities and screening of free carriers, which was observed and compared with previous results.