Wafer-Scale High-Throughput Ordered Arrays of Si and Coaxial Si/Si1-xGex Wires: Fabrication, Characterization, and Photovoltaic Application

We have developed a method combining lithography and catalytic etching to fabricate large-area (uniform coverage overan entire 5-in, wafer) arrays of vertically aligned single. crystal 51 nanowires with high throughput. Coaxial n-Si/p-SiGe-wire arrays are also fabricated by. further coating single-crystal epitaxial SiGe layers on the Si wires using Ultrahigh vacuum chemical vapor deposition (UHVCVD). This method allows precise control over the diameter, length, density, spacing, orientation, shape, pattern and location of Si and Si/SiGe nanowire arrays, making it possible to fabricate an array of devices based on rationally designed nanowire arrays. A proposed.. fabrication mechanism of the etching process is presented. Inspired by the excellent antireflection properties of the Si/SiGe wire arrays, we built solar cells based on the arrays of these wires containing. radial junctions, an example of which exhibits an open circuit voltage (V-oc) of 650 mV, a short-circuit current density (J(sc)) of 8.38 mA/cm(2), a fill factor of 0.60, and an energy conversion efficiency (eta) of 3.26%. Such a p-n radial structure will have a great potential application for cost-efficient photovoltaic (PV) solar energy conversion.