Nanowire Integration Process to Gain Control over Location, Dimension, and Orientation

We report a method to nucleate, grow, and transfer single crystal ZnO with control over location, orientation, size, shape, and final substrate material. The process uses an oxygen plasma treatment in combination with a photoresist pattern on Magnesium doped GaN substrates to define a narrow nucleation region and attachment points with desired 100 nm scale dimensions. Nucleation is followed by lateral epitaxial overgrowth producing single crystals of ZnO with desired size (100 nm – 100 μm) and shape (rods, wires, walls, disks) over 2 inch wafers. The formation of extended uniform arrays of ZnO/GaN heterojunction micro UV LEDs/Solar Cells (2.3 μm on a side) is demonstrated as a first application with light coupling between faceted areas within the equidistantly pitched devices. The quality of the patterned ZnO is high; the commonly observed defect related emission in the electroluminescence spectra is completely suppressed and a single near-band-edge UV peak is observed.