Nanostructuring of GaAs with tailored topologies using colloidal lithography and dry etching

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The authors report on the fabrication of GaAs nanopillars with different profiles/topologies using colloidal lithography and dry etching. GaAs nanopillars with different shapes and dimensions were successfully fabricated using inductively coupled plasma reactive ion etching. Two different etch chemistries CH4/H2/Cl2 and Ar/Cl2 were investigated. The fabricated nanopillar arrays had a typical period of ∼500 nm, and the depths could be varied from a few nanometers to 4 μm. The CH4/H2/Cl2 chemistry with optimized gas flows and plasma powers is shown to produce nanopillars with smooth sidewalls compared to those fabricated with the Ar/Cl2 chemistry. The GaAs nanopillar arrays have appreciably lower reflectivities in the measured wavelength range from 400 to 850 nm and are typically one order of magnitude lower compared to planar GaAs, which shows their potential for photovoltaic applications.