Low-Temperature Growth of ZnO Nanowire Arrays on p-Silicon (111) for Visible-Light-Emitting Diode Fabrication

We report on the successful growth of homogeneous and well-covering ZnO nanowire arrays at a low temperature (90 degrees C) directly on a p-type Si(1 11) wafer by an electrochemical method. The wires were self-standing and vertically oriented. Room-temperature micro-Raman and photoluminescence emission analyses showed the high global structural and optical quality of the material with a low density of deep defects. The ZnO nanowires of the heterostructure were contacted with a transparent ITO electrode, and a light-emitting diode was fabricated. The device current-voltage curve had a rectification magnitude of about 20 at 2.5 V. The threshold forward voltage was low at 1.4 V. The device emitted a broad visible band centered at 590 nm at room temperature under forward bias. According to the energy band diagram of the junction, the emission has been assigned possibly to Si hole injection to near-interfacial ZnO deep levels, followed by the radiative recombination with electrons of the ZnO conduction band.