Diameter Dependent Heating in GaAs Nanowires

The photo-thermal properties of vertically etched gallium arsenide nanowire arrays are examined using Raman spectroscopy. The nanowires are arranged in square lattices with a constant pitch of 400 nm, and diameters ranging from 50 to 155 nm. The arrays were illuminated using a 532 nm laser with an incident energy density of 10 ${\rm W}/{\rm mm}^{2}$. Nanowire temperatures were highly dependent on the nanowire diameter, and were determined by measuring the spectral redshift for both TO and LO phonons. The highest temperatures were observed for the 95 nm diameter nanowires, whose top facets and sidewalls heated up to 600 K and 440 K, respectively, and decreased significantly for the smaller or larger diameters studied. The findings also demonstrate that a photonic lattice consisting of vertically oriented GaAs nanowires allows for optimization of the photo-thermal effect.