Photoluminescence from photochemically etched highly resistive silicon

The photochemical etching method has been performed on n-type Si(111) wafer with a resitivity of 4.2 kOmega cm, in a mixture of HF and H2O2, under He-Ne laser (633 nm) irradiation. The morphology of the porous films grown after exposure to a He-Ne laser at normal incidence were analysed by scanning electron microscopy (SEM). The results show that the films obtained are porous. Furthermore, excitation of the porous silicon layer elaborated from highly resistive silicon samples under He-Cd laser (325 nm) irradiation shows that the porous films are photoluminescent. Photoluminescence of the porous samples was observed only for porosification times approximately or higher than 60 min. It is shown that the PL intensity peak decreases with increasing photochemical etching time. However, a slight shift (blue shift) of the PL peak wavelength is noticed as the etching time increased. In addition, the luminescence spectra are found to be similar to those reported recently for porous Si films produced on silicon of low resistivity. Finally, the quantum confinement effect has been invoked to explain the bright, visible, room temperature PL of PS. (C) 2003 Elsevier B.V. All rights reserved.