Scalable fabrication of nanostructured p-Si/n-ZnO heterojunctions by femtosecond-laser processing

We present a versatile, large-scale fabrication method for nanostructured semi-conducting junctions. Silicon substrates were processed by femtosecond laser pulses in methanol and a quasi-ordered distribution of columnar nanospikes was formed on the surface of the substrates. A thin (80 nm) layer of ZnO was deposited on the laser-processed silicon surface by pulsed laser deposition, forming a nanostructured p-Si/n-ZnO heterojunction. We characterized the structural, optical, and electrical properties of the heterojunction. Electrical I-V measurements on the nanostructured p-Si/n-ZnO device show non-linear electric characteristics with a diode-like behavior. Electrical I-V measurements on a flat p-Si/n-ZnO reference sample show similar characteristics, however the forward current and rectification ratio are improved by orders of magnitude in the nanostructured device owing to its increased surface area. The fabrication method employed in this work can be extended to other homojunctions or heterojunctions for electronic and optoelectronic devices with large surface area.