Effect of electroless etching parameters on the growth and reflection properties of siliconnanowires

Abstract

Vertically aligned silicon nanowire (Si NW) arrays have been fabricated overlarge areas using an electroless etching (EE) method, which involves etching ofsilicon wafers in a silver nitrate and hydrofluoric acid based solution. A detailedparametric study determining the relationship between nanowire morphology and time,temperature, solution concentration and starting wafer characteristics (doping type,resistivity, crystallographic orientation) is presented. The as-fabricated Si NW arrayswere analyzed by field emission scanning electron microscope (FE-SEM) and alinear dependency of nanowire length to both temperature and time was obtainedand the change in the growth rate of Si NWs at increased etching durations wasshown. Furthermore, the effects of EE parameters on the optical reflectivity of theSi NWs were investigated in this study. Reflectivity measurements show thatthe 42.8% reflectivity of the starting silicon wafer drops to 1.3%, recorded for10 µm long Si NW arrays. The remarkable decrease in optical reflectivity indicates that Si NWshave a great potential to be utilized in radial or coaxial p–n heterojunction solar cellsthat could provide orthogonal photon absorption and enhanced carrier collection.