Porous silicon photonic devices using pulsed anodic etching of lightly doped silicon

The fabrication of porous silicon photonic structures using lightly doped, p-type, silicon wafers (resistivity: 14–22 Ω cm) by pulsed anodic etching is reported. The optical properties have been found to be strongly dependent on the duty cycle and frequency of the applied current. All the interfaces of the single layered samples were digitally analysed by calculating the mean interface roughness (Rm). The interface roughness was found to be maximum for the sample with direct current. The use of a duty cycle above 50%, in a certain range of frequencies, is found to reduce the interface roughness. The optical properties of some microcavities and rugate filters are investigated from the optimized parameters of the duty cycle and frequency, using the current densities of 10, 90 and 150 mA cm−2.