Photoluminescence and Raman study of porous silicon synthesized by visible and infrared laser etching

Abstract

Visible and infrared lasers have been used to photochemically fabricate photoluminescent porous silicon thin films on n-type silicon substrates. Photoluminescence measurements on porous silicon exhibit a two-peak structure for argon–ion laser etching. It is found that the intensity ratio for the two photoluminescence peaks at 1.91 and 2.02 eV is reversed on changing the excitation photon energy from 2.41 to 2.71 eV. Etching with a Nd:YAG laser, on the other hand, yields a single PL band. Raman measurements from the two porous silicon samples also show different behavior, both in the location of the peaks, as well as in the asymmetry of Raman lines in first-order spectra. These results are analyzed using a quantum confinement model for photoluminescence and Raman spectra. Mean nanocrystallite size and the size distribution parameters are studied here as a function of excitation energy in the photoluminescence and Raman spectra.