Depth-dependent anti-reflection and enhancement of luminescence from Si quantum dots-based multilayer on nano-patterned Si substrates

Nano-sphere lithography technique was used to fabricate nano-patterned Si substrates with various depths by controlling the etching time. The depth-dependent broadband anti-reflection was observed and the reflectivity could be reduced to 5%. By depositing Si quantum dots/SiO2 multilayer on nano-patterned substrate, the reflection was further suppressed and luminescence intensity was significantly enhanced. The luminescence enhancement is dependent of the etching depth and the luminescence can be one order of magnitude stronger than that on flat substrate due to both the improved absorption of excitation light and the increase of light extraction ratio by nano-patterned structures. (C) 2011 Optical Society of America