Influence of current density on refractive index of p-type nanocrystalline porous silicon

Porous Silicon (PS) layers have been prepared from p-type silicon wafers of (100) orientation. SEM, XRD, FTIR and PL studies were done to characterize the surface morphological and optical properties of PS. The porosity of the PS samples was determined using the parameters obtained from SEM images by geometric method. The refractive index values of the PS samples as a function of porosity were determined by Effective Medium Approximation methods. The influence of current density on porosity and refractive index of PS, were discussed. SEM images indicated that the pores are surrounded by a thick columnar network of silicon walls. This porous silicon layer can be considered as a sponge like structure. The sizes of PS nanocrystallites were determined by XRD studies. FTIR spectra indicated that the porous layer contain SiHn complexes. PL study reveals that there is a prominent emission peak at 606 nm. No spectral shift was observed. These results suggest that this nanocrystalline porous silicon could be a potential candidate for optical as well as optoelectronic device applications.