Photoluminescence blue shift of indium phosphide nanowire networks with aluminum oxide coating

Abstract

This paper describes our finding that optical properties of semiconductor nanowires were modified by depositing a thin layer of metal oxide. Indium phosphide nanowires were grown by metal organic chemical vapor deposition on silicon substrates with gold catalyst resulting in three‐dimensional nanowire networks, and optical properties were obtained from the collective nanowire networks. The networks were coated with an aluminum oxide thin film deposited by plasma‐enhanced atomic layer deposition. We studied the dependence of the peak wavelength of photoluminescence spectra on the thickness of the oxide coatings. A continuous blue shift in photoluminescence spectra was observed when the thickness of the oxide coating was increased. The observed blue shift is attributed to the Burstein–Moss effect due to increased carrier concentration in the nanowire cores caused by repulsion from intrinsic negative fixed charges located at the inner oxide surface. Samples were further characterized by scanning electron microscopy, Raman spectroscopy, transmission electron microscopy, and selective area diffractometry to better understand the physical mechanisms for the blue shift. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Scaling Atomic Layer Deposition to Astronomical Optic Sizes: Low-Temperature Aluminum Oxide in a Meter-Sized Chamber

“…40−43 ALD has become widely popular in materials science applications such as device packaging, semiconductor passivation, transistor gate dielectrics, chemical catalytic surface treatment, optical coatings, energy storage devices, and protective barriers. 28,36,44,45 Several variations of the ALD technique have become standardized industry tools in semiconductor processing for single wafers and wafer batches. 46 Large-area ALD processes have been developed for nonwafer substrates, often utilizing a high-throughput technique known as spatial ALD, 47 with the largest published substrate size of 1.2 m. 48,49 Spatial ALD, in contrast to the temporal ALD process previously described, utilizes the same four step chemistry process by simultaneously running all four steps (TMA pulse, TMA purge, H 2 O pulse, and H 2 O purge) in separated localized zones of a reaction chamber while the substrate to be coated repeatedly moves across the four reaction zones to obtain a desired film thickness.…”

“…Specialized techniques, such as plasma-enhanced ALD, enable an even wider range of material compositions and thin-film properties . The capability of ALD to deposit films on a variety of substrates, including complex high-aspect ratio microstructures and surfaces with different chemical reactivity, has been theoretically analyzed and modeled. , The ultrahigh aspect ratio conformal films deposited by ALD are commonly utilized for various applications including semiconductor processing procedures. − ALD has become widely popular in materials science applications such as device packaging, semiconductor passivation, transistor gate dielectrics, chemical catalytic surface treatment, optical coatings, energy storage devices, and protective barriers. ,,, Several variations of the ALD technique have become standardized industry tools in semiconductor processing for single wafers and wafer batches . Large-area ALD processes have been developed for nonwafer substrates, often utilizing a high-throughput technique known as spatial ALD, with the largest published substrate size of 1.2 m. , Spatial ALD, in contrast to the temporal ALD process previously described, utilizes the same four step chemistry process by simultaneously running all four steps (TMA pulse, TMA purge, H 2 O pulse, and H 2 O purge) in separated localized zones of a reaction chamber while the substrate to be coated repeatedly moves across the four reaction zones to obtain a desired film thickness.…”