  We present a versatile, large-scale fabrication method for nanostructured
semiconducting 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. The fabrication
method employed in this work can be extended to other homojunctions or
heterojunctions for electronic and optoelectronic devices with large surface
area.
