Assoc. Prof. Patrick Parkinson, University of Manchester - A needle in a needlestack – exploiting functional inhomogeneity as a tool for optimized nano-optoelectronics

Semiconductor nanomaterials – where one or more dimensions lie in the sub-micron regime – are now widely studied as a route to create novel or enhanced optoelectronic materials. From colloidal quantum dots to VLS-grown nanowires, these materials provide opportunities through controlled light-matter coupling and high surface-area-to-volume ratio. Functional nanomaterials combine multiple features to meet specific applications in photovoltaics, light emission, lasing or sensing by exploiting this geometry. A particular opportunity is provided by bottom-up growth of nanomaterials, generating huge numbers of near-identical nanoscale objects through thermodynamically driven processes.

However, growth at the nanoscale is vulnerable to inhomogeneity. Heterogeneity in morphology (shape), geometry (size), crystal structure (polytypism), doping, strain, and defect density are inherent to nanofabrication, and these may have a large and non-linear impact on functional performance (such as IQE or lasing threshold). I will describe a high-throughput methodology to study inhomogeneity in nanowires, and its use to both optimize and exploit variability. By studying large numbers of single wires (10k-100k), recombination routes, carrier mobility, doping and even sub-picosecond dynamics can be extracted using simple photoluminescence techniques.

Patrick Parkinson is a senior lecturer (Associate Professor) in the Department of Physics and Astronomy at the University of Manchester. Since 2020 he has led a UKRI-funded program on “Big-data for nanoelectronics”, combining high-throughput techniques with functional nanomaterials to build statistically rigorous models. This project includes academic and industrial partners in the UK, China, Australia, Germany, Israel and Sweden. He has previously worked in postdoctoral roles at the University of Oxford and the Australian National University, in Physics, Chemistry and Electronic Materials departments. He completed his PhD in Organic-Inorganic Optoelectronic Nanomaterials with Prof. Laura Herz at the University of Oxford in 2009.

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Prof. Hannah Joyce, University of Cambridge - Growth, characterisation and device integration strategies for III-V nanowires

The non-planar nature of free-standing III–V nanowires creates new opportunities for electronic and optoelectronic device architectures, but also necessitates new strategies for nanowire growth, characterisation and integration. This presentation will discuss these strategies. The growth parameters for catalyst-free and silane-assisted III–nitride nanowire growth by metalorganic vapour phase epitaxy will be discussed. Surface modifications and passivation, achieved either during growth or post-growth, are also necessary for achieving reproducible device performance. We will present the development of a multiplexer chip capable of addressing single-nanowire transistors in arrays. Nanowires, deterministically positioned on the multiplexer by transfer-printing, exhibited reproducible electrical behaviour and high device yield. The multiplexer’s ability to operate from room temperature down to milliKelvin temperatures enables the study of quantum phenomena in multiple and interconnected nanowire devices. A promising route towards flexible electronics involves embedding nanowires in a transparent polymer host matrix. By judicious choice of polymer type and deposition conditions, the encapsulated nanowire array preserves the as-grown orientation of the nanowires and can be removed from the rigid growth substrate, creating a flexible and robust device while permitting re-use of the substrate for subsequent growths. This process technique has been used to create flexible terahertz modulator devices based on arrays of aligned GaAs nanowires

Hannah Joyce is a Professor in low-dimensional electronics at the University of Cambridge. In 2013, Hannah joined the Department of Engineering at the University of Cambridge, after completing her PhD at the Australian National University and after completing her postdoc at the University of Oxford. In Cambridge she leads a research group focussing on the development of novel nanomaterials for applications in photonics and electronics. Her interests span the growth of novel low-dimensional semiconductor materials, the development of terahertz spectroscopy for contact-free characterisation of nanomaterials, and the development of new nanomaterial-based devices such as photovoltaics, photodetectors and terahertz photonic modulators.