Wavelength-Dependent Absorption in Structurally Tailored Randomly Branched Vertical Arrays of InSb Nanowires

Abstract

Arrays of semiconductor nanowires are of potential interest for applications including photovoltaic devices and IR detectors/imagers. While nominally uniform arrays have typically been studied, arrays containing nanowires with multiple diameters and/or random distributions of diameters could allow tailoring of the photonic properties of the arrays. In this Letter, we demonstrate the growth and optical properties of randomly branched InSb nanowire arrays. The structure mentioned can be approximated as three vertically stacked regions, with average diameters of 20, 100, and 150 nm within the respective layers. Reflectance and transmittance measurements on structures with different average nanowire lengths have been performed over the wavelength range of 300-2000 nm, and absorbance has been calculated from these measurements. The structures show low reflectance over the visible and IR regions and wavelength-dependent absorbance in the IR region. A model considering the diameter-dependent photonic coupling (at a given wavelength) and random distribution of nanowire diameters within the regions has been developed. The diameter-dependent photonic coupling results in a roll-off in the absorbance spectra at wavelengths well below the bulk cutoff of ∼7 μm, and randomness is observed to broaden the absorbance response. Varying the average diameters would allow tailoring of the wavelength dependent absorption within various layers, which could be employed in photovoltaic devices or wavelength-dependent IR imagers.

Electrodeposition of InSb branched nanowires: Controlled growth with structurally tailored properties

“…In prior studies, we have characterized the average pore diameters and distribution of diameters within each region. 36 The working electrode for the cyclic voltammetry experiment and the electrochemical deposition process was formed by evaporating a 100 nm Au layer on the surface of the PAA template containing the random branched structure. A three-electrode electrochemical cell with a Pt-mesh counter electrode, and an Ag/AgCl (saturated 3 M NaCl) reference electrode (0.175 V vs. Normal Hydrogen Electrode (NHE)) was employed.…”

“…These new nanophotonic physics in subwavelength scale can readily be exploited in efficient photon managements in number of applications such as photovoltaics, photocatalysis, and IR detectors. 36,55 FIG. 9.…”

Recent advances in antireflective surfaces based on nanostructure arrays

“…67 An interesting randomly branched vertical array of InSb nanowires was obtained by Mohammad et al via electrodeposition within branched porous anodic alumina membranes, which exhibited low reectance over the visible and IR regions as well as wavelength-dependent absorbance in the IR region. 68 GaAs nanopyramids prepared by using a combination of nanosphere lithography, nanopyramid metal organic chemical vapor deposition (MOCVD) growth, and gas-phase substrate removal processes showed excellent optical absorption over a broad range of wavelengths, at various incident angles and at largecurvature bending. 69 Besides the vapor growth method, the top-down etching (mainly the dry etching technique) was also a very effective approach for fabricating NSAs of group III-V semiconductors as AR coatings.…”

Rapid, facile synthesis of InSb twinning superlattice nanowires with a high-frequency photoconductivity response

“…28 Among the known binary III-V compound semiconductors, indium antimonide (InSb) has a narrow direct band gap energy (0.17 eV), low thermal conductivities (0.18 W cm À1 K À1 ), small exciton binding energy (0.5 meV), and extremely high electron mobilities (78 000 cm 2 V À1 s À1 ) at room temperature, 29,30 consequently making it the suitable material for infrared photodetectors, topological superconductivity and a promising platform for quantum computing. [31][32][33] To date, InSb nanowires have been generally synthesized by epitaxial growth methods (>400 C) including metal-organic vapor phase epitaxy (MOVPE), 34,35 chemical beam epitaxy (CBE) and molecular beam epitaxy (MBE) via the vapor-liquid-solid (VLS) mechanism. [36][37][38][39] However, the growth of InSb twinning superlattice nanowires by the above-mentioned methods has proven to be very challenging primarily attributed to the small ionicity with low bonding tendency and the high energy barrier (8.2 meV per atom) for the ZB/WZ phase transition compared with other III-V compound semiconductor nanowires.…”