Epitaxial Growth of Aligned Semiconductor Nanowire Metamaterials for Photonic Applications

Abstract

We present a novel class of optical metamaterials consisting of high densities of aligned gallium phosphide (GaP) nanowires fabricated using metal-organic vapor phase-epitaxy. Starting from a gold island film as a catalyst for nanowire growth, a sequential combination of vapor-liquid-solid and lateral growth modes is employed to obtain a continuous tunability of the nanowire volume fraction from 7% to over 35%. By choosing different crystallographic orientations of the GaP substrate, we design metamaterials with different nanowire orientations. The anisotropy of the nanowire building blocks results in strong optical birefringence. Polarization interferometry demonstrates a very large polarization extinction contrast of 4×10 3 combined with a sharp angular resonance which holds promise for optical sensing. Nanowire metamaterials may find applications in photonics, optoelectronics, non-linear and quantum optics, microfluidics, bio-, and gas sensing.

Large Photonic Strength of Highly Tunable Resonant Nanowire Materials

“…The growth of GaP nanowires has been well characterized for various conditions and substrates. 23,24 Nanowires were grown using a metalloorganic vapor epitaxy following the method of ref 20. A combination of vapor-liquid-solid (VLS) and lateral growth processes was used to precisely tune the diameter of the wires while keeping the nanowire density fixed.…”

“…For wire diameters below 40 nm, no coherent backscattering is observed because these samples are weakly scattering. 20 All cones were normalized to a Teflon reference sample with a negligible EBS contribution, after which the diffuse background was subtracted from the enhanced backscattering. This choice of normalization is most suited for visualization of the gradual buildup of the EBS cone with increasing scattering strength.…”

Design of Light Scattering in Nanowire Materials for Photovoltaic Applications

“…Alternatively, suppression of light scattering can be achieved by reducing the diameter of the nanowires below 30 nm. 15 Such a reduction will pose challenges with respect to the electronic properties of the nanowires, such as full wire depletion. It may also be possible to utilize an entirely different regime of micrometer-sized pillars, where light can be trapped by multiple reflections at the surface texture.…”

Second-Order Scattering Induced Reflection Divergence and Nonlinear Depolarization on Randomly Corrugated Semiconductor Nano-Pillars

“…In most works, the surface anti-reflection property of the nano-roughened structure was typically realized as a multi-layered model with gradually changed refractive index induced by different air-Si mixture compositions [8]. In addition, the investigation of light scattering from the roughened anti-glare surface has caused great interests in scientific researches [9][10][11][12][13][14][15][16]. In 1967, the surface depolarization on the backscattered light from either the disordered metallic or inhomogeneous dielectric surfaces under a linearly polarized incidence at different angles were experimentally characterized without theoretical modeling [9].…”