Controlled faceting and morphology for light trapping in aluminum-catalyzed silicon nanostructures

Aluminum-catalyzed silicon nanopyramids grown using low-pressure chemical vapor deposition (LPCVD) are presented as an approach to silicon surface texturing. The nanopyramids are grown by vapor-liquid-solid growth using aluminum thin films on silicon. Silicon nanowires with hexagonal cross-sections are formed at a growth temperature of 650 °C; as the temperature is increased to 700 °C, the wires become pyramid-shaped with triangular cross-sections. The silicon nanopyramids are single-crystal and grow in the <111>direction with (112) facets, as confirmed by transmission electron microscopy. Pyramid tapering increases with increasing growth temperatures and the pyramid arrays grown at 700 °C show reflectivities between 4 and 6% between 400 nm and 800 nm and appear black to the eye. Based on these results, aluminum-catalyzed nanopyramids present themselves as a plausible alternative to etch-based silicon surface textures.