Subwavelength scale antireflection moth-eye structures in silicon were fabricated by a wafer-scale nanoimprint technique and demonstrated an average reflection of 1% in the spectral range from 400 to 1000 nm at normal incidence. An excellent antireflection property out to large incident angles is shown with the average reflection below 8% at 60°. Pyramid array gave an almost constant average reflection of about 10% for an incident angle up to 45° and concave-wall column array produced an approximately linear relation between the average reflection and the incident angles. The technique is promising for improving conversion efficiencies of silicon solar cells.

This version is available at https://strathprints.strath.ac.uk/42421/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Abstract: Hyperspectral cathodoluminescence imaging provides spectrally and spatially resolved information on luminescent materials within a single dataset. Pushing the technique toward its ultimate nanoscale spatial limit, while at the same time spectrally dispersing the collected light before detection, increases the challenge of generating low-noise images. This article describes aspects of the instrumentation, and in particular data treatment methods, which address this problem. The methods are demonstrated by applying them to the analysis of nanoscale defect features and fabricated nanostructures in III-nitride-based materials.

In x Ga 1Àx N/GaN quantum wells have been grown on the f10 11g facets of dense arrays of self-assembled GaN nano-pyramids formed by selective area growth and characterised by high spatial resolution cathodoluminescence. The pyramids are shown to have significantly reduced defect (green-yellow) band emission and the quantum well luminescence is correspondingly intense. The peak energy of this luminescence is shown to blue-shift as the sampled region is moved up the pyramid facets, revealing that InN incorporation in such closely spaced epitaxial nanostructures differs from that in widely spaced micron-size pyramidal structures decreasing rather than increasing towards the nano-pyramid tips. #

Multi-wavelength in situ reflectometry at normal incidence has been applied to monitoring metal organic vapour phase epitaxy of GaN films on sapphire (0 0 0 1) substrates. A new quantitative analysis model has been developed to incorporate time-dependent light scattering by a rough surface, and a time-dependent vertical growth rate during growth on a rough surface, into the virtual interface model that has previously been applied to multilayer structures with optically smooth surfaces and interfaces. It is shown that the vertical growth rate increases as the surface roughness decreases in the early stage of high-temperature GaN growth, reaching a limiting value when the surface becomes optically smooth. The time dependence of growth rate is correlated with microscopic crystal growth mechanisms on the rough surface, which involve mass transport on the facets and/or mass exchange between the growing surface and gas-phase ambient. Our optical modelling is supported by direct morphological investigations of films from growths terminated at various stages, using atomic force microscopy. High-temperature optical constants of GaN layers extracted from the simulations are well matched to literature values.

The growth behaviour of GaN selective area growth (SAG) by MOVPE on two types of nano‐patterned GaN substrates has been investigated. Samples were characterized by SEM, AFM and TEM. Results indicate that well formed nano‐pyramids with base size of ∼150 nm, and sharp tips are readily grown through mask patterns defined by electron beam lithography (EBL). A growth rate of nearly zero on the {10$ \bar 1 $1} nano‐facets, effectively self‐limiting growth (SLG), has been observed under a wide range of growth conditions using a conventional growth mode. In contrast, pulsed growth is able to change the SLG behaviour, and thereby control the size of pyramids, even to coalesce the pyramids to form flat, smooth GaN films. SLG‐like behaviour of GaN SAG on patterns defined by nano‐imprint lithography (NIL) is also observed and enabled nano‐pyramids to form. However, GaN SAG on NIL patterns shows accelerated growth in some pores at the early stage of the growth. This accelerated growth is attributed to the possible presence of screw‐type dislocations in the pore. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)