In this presentation, we present a simple methodology for formation and hierarchical assembly of electrically addressable nanowire-based semiconductor heterojunctions. These p-n junctions are oriented and formed epitaxially by planar growth of nanowires on a semiconductor substrate, as opposed to conventional approaches that use mechanical contacts. We demonstrate a practical two-step approach for scalable electrical injection into these nanowire heterojunctions. The formed heterojunctions are grown from arrays of zinc oxide nanowires and nanowalls on a semiconductor substrate. We show their blue and orange-color light emissions depending on the polarity of the applied voltage. The developed architecture could be a general methodology for fabricating addressable assemblies of nanowires useful in photovoltaics and photodetectors.