New Paper : Facet-Related Non-uniform Photoluminescence in Passivated GaAs Nanowires

(Left) SEM image of a single 250nm diameter GaAs nanowire with {112} facets highlighted and (Right) recombination measured in the {110} region (blue) and {112} region (red), showing emission quenching at these surfaces.

Our collaborative work on spatially inhomogeneous recombination in semiconductor nanowires has been published in a special issue of Frontiers in Chemistry. The work, led by Dr. Nian (Jenny) Jiang at the University of Cambridge reports the spatially varying emission intensity from passivated nanowires. By comparing the bulk emission to buried quantum well emission, we show that the a reduction in emission is related to {112}-faceted surfaces at the base of the wires.

This work solves a long-standing question in optoelectronic nanowires – why does the emission vary for nominally uniform structures? It provides two routes to avoiding this variation, through quantum well emission and by tuning the surface reconstruction to favour {110} side-walls.

Reference: Facet-Related Non-uniform Photoluminescence in Passivated GaAs Nanowires, Nian Jiang, Hannah Joyce, Patrick Parkinson, Jennifer Wong-Leung , Hark Hoe Tan and Chennupati Jagadish, Frontiers in Chemistry, 8, 1136 (2020), DOI: 10.3389/fchem.2020.607481

New Paper: Carrier dynamics and recombination mechanisms in InP twinning superlattice nanowires

(a) Twinning superlattice nanowire on substrate, (b) high-resolution SEM and (c) TEM image showing superlattice.

A new paper has been published in Optics Express, led by collaborator Xiaoming Yuan at Central South University (Changsha) and growth colleagues in the group of Prof. Jagadish at Australian National University.

In this work, novel “twinning-superlattice” nanowires are grown. Once passivated, this growth method produces extremely high quality nanowires, with carrier lifetimes of over 7ns. This work made use of the Manchester iTCSPC spectrometer, built by group PhD student Stefan Skalsky to study the low fluence dynamics at room temperture.

This growth method opens up a new facet in crystal-phase engineering for nanowire optoelectronics.

Reference: Carrier dynamics and recombination mechanisms in InP twinning superlattice nanowires, Xiaoming Yuan, Kunwu Liu, Stefan Skalsky, Patrick Parkinson, Long Fang, Jun He, Hark Hoe Tan, and Chennupati Jagadish, Optics Express 28, 16795 (2020) DOI: 10.1364/OE.388518

New Paper: Characterisation, Selection and Micro-Assembly of Nanowire Laser Systems

Our collaborative work on the selection, transfer and testing of semiconductor nanowire lasers has now been published in Nano Letters.

In this work, growth colleagues at ANU prepared nanowire lasers which were characterised at Manchester. This characterisation was used to select bins of nanowires, which were transferred using a cutting edge pick-and-place tool at the University of Strathclyde. The transferred wires were re-tested in Manchester; while some wires showed identical behaviour, some showed a change in lasing mode.

This work will guide the heterointegration of nanowire lasers with photonic circuits, targetting high-yield and industrial applicability.

Reference: Characterisation, Selection and Micro-Assembly of Nanowire Laser Systems, Jevtics et al., Nano Letters (ASAP), DOI: 10.1021/acs.nanolett.9b05078

New Paper – Optical Study of p-Doping in GaAs Nanowires for Low-Threshold and High-Yield Lasing

Our new work on large-scale statistical spectroscopy to optimize nanowire lasers is published today in Nano Letters. In this work, PhD student Arturo studied thousands of nanowires to identify the lowest threshold nanowire, as well as to model emission to identify the primary sources of non-radiative emission.

By quickly sorting nanowires by doping and length, he was able to demostrate sub-sets with over 90% yield and class-leading thresholds, pointing the way towards electrically injected nanolasers.

Congratulations Arturo!

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(Left) Far-field emission from a record breaking nanowire laser, emitting at room temperature and low exciation levels. (Right) Doping vs Quantum efficiency, showing two key limiting behaviours.

Reference: “Optical Study of p-Doping in GaAs Nanowires for Low-Threshold and High-Yield Lasing”, Juan Alanis et al., Nano Letters, ASAP 2018, DOI: 10.1021/acs.nanolett.8b04048

New Publication – Distinguishing cap and core contributions to the photoconductive terahertz response of single GaAs based core–shell–cap nanowire detectors

corecap.pngOur recent work on single-nanowire terahertz detectors has been published in a special issue of the Lithuanian Journal of Physics, celebrating the 70th birthday of Prof. Arunas Krotkus.

In this work, Dr Kun Peng used single-nanowire terahertz detectors with different capping to understand the relative contribution of the core and cap to the detected THz signal. By tuning the cap to be thicker, it is possible to engineer these detectors to have shorter carrier lifetimes and as a result, to exhibit direct THz field detection.

New Publication – Large-scale statistics for threshold optimization of optically pumped nanowire lasers

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Arturo’s recent work has been published in Nano Letters [at  http://pubs.acs.org/doi/10.1021/acs.nanolett.7b01725 ]. This work was done in collaboration with the group of Professor Chennupati Jagadish at the Australian National University.

In this paper, we describe how automated and high-speed spectroscopy can be applied to nanomaterials to collect sufficient data to apply statistical techniques. Using this approach, we are able to use the inherent spread in parameter space which arises from bottom-up growth techniques to provide pointers to future optimization.

Importantly, we also reveal that for a specific growth of semiconductor nanolasers, we are able to achieve yields of over 50% and lowest pump thresholds of 42μJ/cm2, a record for room-temperature near infra-red nanolasers.

Congratulations Arturo!

New Publication – Single n-i-n InP Nanowires for Highly Sensitive Terahertz Detection

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Kun Peng has written a paper accepted in IOP Nanotechnology (http://iopscience.iop.org/article/10.1088/1361-6528/aa5d80).

The work, building on previous progress in single nanowire terahertz detectors, uses a combination of an axial doping profile and novel optical characterisation to improve the contact quality for these devices.

The new nanowire detectors show improved signal-to-noise ratio, now approaching that of conventional detectors.

 

New Paper – Broad Band Phase Sensitive Single InP Nanowire Photoconductive Terahertz Detectors

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Kun’s paper “Broad Band Phase Sensitive Single InP Nanowire Photoconductive Terahertz Detectors” has been accepted for publication in Nano Letters. In the work, Kun has fabricated a single nanowire terahertz detector using an InP nanowire, and compared different antenna structures with traditional “bulk” InP detectors.

We have shown the utility of these structures for terahertz detection with a source limited bandwith, opening up possibilities for nanoscale terahertz electronics.

The paper, a collaboration between the University of Oxford Terahertz Photonics Group (Johnston Group), the Australian National University Electronic Materials Engineering Group (Jagadish Group) and the Parkinson Group at the University of Manchester is currently “just accepted”, and available at http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b01528.

Conference – ICONN 2016

Patrick has given a talk at ICONN 2016 (the International Conference on Nanoscience and Nanotechnology), held in Canberra, Australia.

The conference had sessions focussing on nanophotonics, nanomaterials, nanocharacterisation, nanoelectronics and commercialisation/safety issues. Patrick spoke on “Statistical Study of Nanowire Disorder”, covering new work as well as Christopher Davies recent Nanoscale publication.

Additionally it was an opportunity to catch up with collaborators at the Australian National University – A/Prof Fu Lan, Prof Hoe Tan and Prof Chennupati Jagadish. It was particularly good to celebrate Prof. Jagadish’s recent award of Australia’s highest civilian honour, the Companion of the Order of Australia.

While it was great to meet up with old collaborators and friends, it was less fun to catch up with Canberra’s other natives…

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