Abstract
Ion sputtering assisted formation of nanopillars is demonstrated as a wafer-scale, lithography-free fabrication method to obtain high optical quality gallium indium phosphide (GaInP) nanopillars. Compared to binary materials, little has been reported on the formation of self-organized ternary nanostructures. Epitaxial (100) Ga0.51In0.49P layers lattice matched to GaAs were sputtered by nitrogen (N2) ions with relatively low ion beam energies (∼400 eV) to reduce ion bombardment induced damage. The influence of process parameters such as temperature, sputter duration, ion beam energy, and ion beam incidence angle on the pillar formation is investigated. The fabricated GaInP nanopillars have average diameters of ∼75–100 nm, height of ∼220 nm, and average density of ∼2–4 × 108 pillars/cm2. The authors show that the ion beam incidence angle plays an important role in pillar formation and can be used to tune the pillar shape, diameter, and spatial density. Specifically, tapered to near cylindrical pillar profiles together with a reduction in their average diameters are obtained by varying the ion beam incidence angle from 0° to 20°. A tentative model for the GaInP nanopillar formation is proposed based on transmission electron microscopy and chemical mapping analysis. μ-Photoluminescence and μ-Raman measurements indicate a high optical quality of the c-GaInP nanopillars.
Highlights
Semiconductor nanopillars/wires can be used for a wide variety of applications in the fields of, e.g., optoelectronics and sensing.1–4 They offer unique features for obtaining specific optical functions, e.g., light extraction, increased absorption, and optical nonlinearity
Wafer-scale, self-organized gallium indium phosphide (GaInP) nanopillars were obtained based on an ion beam sputtering (IBS) process using low energy (∼400 eV) nitrogen (N2) ions
High optical quality crystalline GaInP (c-GaInP) nanopillar assemblies were obtained with an average pillar diameter of ∼75–100 nm, height of ∼220 nm, and average density of ∼2–4 × 108 pillars/cm2
Summary
Semiconductor nanopillars/wires can be used for a wide variety of applications in the fields of, e.g., optoelectronics and sensing. They offer unique features for obtaining specific optical functions, e.g., light extraction, increased absorption, and optical nonlinearity. III–V semiconductors, e.g., indium phosphide (InP) and gallium arsenide (GaAs), have the benefit of a direct bandgap, large absorption coefficients, and high conversion efficiencies Nanostructuring of these III–V materials paves the way for implementing light manipulation functions, e.g., trapping, guiding, and antireflection. Recent works investigated the species that should be present on the nanostructure top for binary compounds (based on sputtering yield and diffusivity), where Shipman and Bradley developed a theory for ordered nanodot formation based on normal incidence ion bombardment These works indicate that element segregation may occur after ion beam processing and that ex situ characterization may provide distorted information. IBS pattern formation of III–V semiconductor materials is interesting due to their rapid formation rate, high aspect ratio structures due to low saturation, the occurrence of dense patterns over large surface areas, and enhanced growth rate for increasing temperatures.. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDS), μ-photoluminescence (PL), and μ-Raman measurements were used to characterize the fabricated GaInP nanopillars
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