Highly ordered vertical GaAs nanowire arrays with dry etching and their optical properties

Abstract

We report fabrication methods, including metal masks and dry etching, and demonstrate highly ordered vertical gallium arsenide nanowire arrays. The etching process created high aspect ratio, vertical nanowires with insignificant undercutting from the mask, allowing us to vary the diameter from 30 nm to 400 nm with a pitch from 250 nm to 1100 nm and length up to 2.2 μm. A diameter to pitch ratio of ∼68% was achieved. We also measured the reflectance from the nanowire arrays and show experimentally diameter-dependent strong absorption peaks resulting from resonant optical mode excitations within these nanowires. The reflectance curves match very well with simulations. The work done here paves the way towards achieving high efficiency solar cells and tunable photodetectors using III–V nanowires.

Self-catalyzed molecular beam epitaxy growth and their optoelectronic properties of vertical GaAs nanowires on Si(111)

“…Typically, vertical GaAs nanowires can be grown on Si(111) substrate using Ga droplet as a catalyst via vapour-liquid-solid (VLS) mechanism by molecular beam epitaxy (MBE) [23][24][25][26]. However, non-vertical and non-uniform wires are frequently occurred when III-V nanowires were grown on Si(111), resulting from the possibility of initiating non-vertical NW growth on the oxide layer without direct contact with the underlying Si [26,27].…”

Localized absorption in aluminum mask in visible spectrum due to longitudinal modes in vertical silicon nanowire arrays

“…They act as nucleation catalysts in their Vapor-Liquid-Solid (VLS) growth [15][16][17] or as protective masks in dry etching. 11,18,19 They are usually removed at the end of the growth or etching of the nanowires. 11 In some cases, it is not feasible or necessary to remove them, especially, when they do not significantly change the optical properties of the nanowires.…”

Elongated nanostructures for radial junction solar cells

“…The top-down method is to etch a mask covered bulk material to form NWs [38]. Lithographic techniques and dry etching are commonly used [39]. This method has limitations in making small NWs, especially for the ones with diameter smaller than 10 nm.…”

“…But due to the lack of staking faults and the high-quality NW/substrate interface, it has gained great attention [40]. Dhindsa et al achieved highly ordered vertical gallium arsenide NW arrays by this method (figure 1(a)) [39]. On the other hand, the bottom-up method can fabricate NW in the angstrom level and offer better ability to handle strain [1].…”