Investigation of photoluminescence efficiency of n-type porous silicon by controlling of etching times and applied current densities

Photoluminescence properties and surface morphologies of porous silicon were investigated by controlling of etching times and applied current densities. FE-SEM image of porous silicon surface indicated that the porous silicon prepared at currents below 200mA/cm^2 exhibited very stable and even surface. However the porous silicon prepared at currents above 300mA/cm^2 displayed the cracked surface of porous silicon. This cracked surface was collapsed to give cracked domains at currents over 500mA/cm^2. Photoluminescence of porous silicon was investigated by controlling of etching times and applied current densities in the range from 50 to 900s and from 50 to 800mA/cm^2, respectively. Photoluminescence intensity of porous silicon increased gradually during etching process, reached maximum, and then decreased as the etching time increased. Porous silicon showed the best photoluminescence efficiency was prepared at currents of 200mA/cm^2 and etching time of 300s.