Development and Application of Non-Equilibrium Doping in Amorphous Chalcogenides

Lead Research Organisation: University of Manchester
Department Name: Electrical and Electronic Engineering

Abstract

In the 20th century, the development of silicon-based electronics revolutionised the world, becoming the most pervasive technology behind modern-day life. In the 21st century, it is envisaged that technology will move to the use of light (photons) together with, or in place of, electrons, providing a dramatic increase in the speed and quantity of information processing whilst also reducing the energy required to do so. Making this transition to an all optical 'photonic' technology has proved to be a complex task, as the material of choice for electronics, silicon, is limited in its ability to control light. In the search for alternative materials, a class of glasses called amorphous chalcogenides (a-ChGs) have shown remarkable promise, to the point where they have been referred to as the 'optical equivalent of silicon'. Chalcogenides are materials which contain one or more of the elements sulfur, selenium or tellurium as a major constituent. These materials are already widely used in applications such as photovoltaics, memory (e.g. DVDs), advanced optical devices (e.g. lasers), and in some thermoelectric generation systems. It is accepted that the move to all-optical technologies will require an intermediate stage where information processing is undertaken using a hybrid 'optoelectronic' system. This provides a strong and compelling argument for the development of a-ChGs, as they can be deposited on Si to form a hybrid approach en-route to their use as an all-optical platform.

Whilst the optical properties of a-ChGs may be controlled and modified it has proved to be extremely difficult to modify their electronic properties during the material preparation, which has typically involved melting at high temperatures. Any impurities that are added to these materials in order to change the electronic behaviour are ineffective under these conditions due to the ability of the ChG material to reorder itself when melted, and so negate the desired doping effect. We have successfully pioneered a method to modify their properties by introducing dopants into a-ChGs below their melting temperature, thus not allowing the material to reorder, using ion-implantation. This method of doping allows precise control of the type of impurity introduced and is widely used in silicon technologies. As a result of this work, we have demonstrated the ability to reverse the majority charge carrier type from holes (p-type) to electrons (n-type) in a spatially localised way. This step-changing achievement enabled us to demonstrate the fabrication of optically active pn-junctions in a-ChGs, which will act as the enabling catalyst for the development of future photonic technologies.

In this project we will seek to develop a full understanding of the process of carrier-type reversal on the atomic scale, and use this information to optimize it, and the materials that are to be modified, so as to add further functionality. We will also develop the required advanced engineering methods which relate to the control and activation of dopants introduced using ion-implantation into a-ChGs. Together, these will enable the demonstration of a series of optoelectronic devices demonstrating the key functionalities required to build an integrated optoelectronic technology.

This programme will consolidate the position of the UK as the world leader in the field of non-equilibrium doping of chalcogenides. We will, in this way, champion these materials in the world's transition to beyond CMOS technology and therefore directly contribute to the continuing growth of the knowledge economy. We will train the next generation of scientists and engineers in state-of-the-art techniques to ensure that the UK maintains the expertise base required for this purpose, aim to ensure that the impact of this work is maximised and accelerated where possible, and communicate the results widely, including to all stakeholders in this research.

Planned Impact

Who will benefit from the research?

The development of advanced materials and future technologies in optoelectronics and photonics is critical for enabling future advances in communications and computing, information handling and the 'internet of things', energy harvesting and storage, healthcare, sensing and even quantum technologies where the control and distribution of entangled light is required.

a-ChGs are already utilised by industry in thin-film and optical fibre waveguides, for light switching, as an optically pumped laser host, whilst from an electronic aspect they are a key component in phase-change memory. In research environments they are at the forefront of the development of optical memory and logic. Our recent work has significantly advanced their potential and importance in terms of functionality with the ability to form pn-junction devices providing a step-change in potential capability. We strongly believe that the work that we propose will be of direct benefit to both industry and researchers alike. Initially, industrial benefit will be in the photonics and micro-electronics fields and related industries where our patent filing[3] may be exploited. Micro-electronics is a vast, pervasive market that has continued to grow at 5% each year since 2000. As the benefits of photonic technologies, a $375 billion global market in 2013, are further realised, new disruptive innovations are required for their full potential to be reached. It is said that the 20th century was the 'century of the electron' and that the 21st century can become the 'century of the photon'. Indeed, the United Nations has declared 2015 as the International Year of Light and Light-Based Technologies.[38] A-ChGs have been described as the 'optical equivalent of Si' and therefore may provide the enabling platform technology to achieve this aim.

Such broad-ranging impact will be of benefit to a wide range of stakeholders and end users, outside of academia and industry, including funders of research and policy makers, government, healthcare institutions and those delivering it, education, the 'third sector' and the wider public, and the UK.

How will they benefit from this research?

Having initiated and been involved in defining the challenges we are addressing, funding bodies and stakeholders that they represent will benefit from the progress we make. The outcome of our research will inform and provide direct support for future research-programme prioritisation relating to these challenges. As we develop new materials and technologies, other funders of research in different discipline areas will also benefit as the outcomes are translated into applications elsewhere.

Those developing future technologies and undertaking research and development in industry will benefit from this project. The a-ChG devices and integrated optical chips which we will demonstrate will provide the evidence required to justify new research programmes offering a novel approach to the development of new technologies. The realisation of the materials, effects, and devices envisaged within the programme will be transformational on the field in the short-term, setting the agenda internationally. On a longer timescale as all-optical integrated photonic systems are realised and move into production, the impact on quality of life, manufacturing, and the economy will be dramatic, as reflected by the high level of interest in enabling all-optical technologies at both national and international levels.

The UK will benefit from the research undertaken not only through the above contributions (and those described in the pathways to impact) to policy, industry, education etc., but by the consolidation of its current position in leading the development of next-generation a-ChG technologies via a world-leading research programme. This will translate into the wider benefits of increased competitiveness in research and development, attracting further talent to the UK.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
EP/N020057/1 01/04/2016 30/11/2016 £381,101
EP/N020057/2 Transfer EP/N020057/1 01/01/2017 31/10/2019 £337,620
 
Description Advances in the understanding of the fundamental properties of amorphous chalcogenides have taken place. These include the measurement of the electrical and photonic properties under various conditions with the aim of improving their performance. The results of these studies will be published in peer-reviewed journals and presented at international conferences.
Exploitation Route The findings will be exploited by those developing new technologies and materials systems based on amorphous chalcogenide semiconductors.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics

 
Description Platform for Nanoscale Advanced Materials Engineering (P-NAME)
Amount £702,172 (GBP)
Funding ID EP/R025576/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 03/2018 
End 09/2020
 
Description SK Saskatoon 
Organisation City, University of London
Department Electrical and Electronic Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Provision of research samples and access to research facilities.
Collaborator Contribution Provision of research samples and access to research facilities.
Impact Exchange of samples and research visit exchanges.
Start Year 2016
 
Description Smart Materials for Data Storage 
Organisation Ilika
Department Ilika Technologies Ltd.
PI Contribution HAMR is a technology designed to enable the next big increase in the amount of data that can be stored on a hard drive. It uses a new kind of media magnetic technology on each disk that allows data bits, or grains, to become smaller and more densely packed than ever, while remaining magnetically stable. A small laser diode attached to each recording head heats a tiny spot on the disk, which enables the recording head to flip the magnetic polarity of each very stable bit, enabling data to be written. Our research team provided expertise in our knowledge of advanced materials to the industrial partner Seagate to help them indentify materials more suitable in the hard drives they were developing.
Collaborator Contribution The Nanomaterials for Data Storage project has successfully demonstrated new materials with new capabilities to improve read write transducer reliability and performance in next generation hard drive products. High thermal conductivity materials have been processed at Seagate's wafer fabrication facility with follow on electrical testing to verify that the nitride based materials have enabled reduced thermal effects in the transducer, translating into a 25% gain in the ability to set the distance between the head and the disk. This will enable reduced time to product launch for the Heat Assisted Magnetic Recording (HAMR) hard drive technology due to reach the market in early 2019. Advanced material synthesis and test capability at the partner organisations, Ilika and University of Southampton was used to facilitate material optimisation and exploration with many alternative options. The Nanomaterials for Data Storage has resulted in strong working relationship between Seagate, llika and the University of Southampton. As a result of this another Innovate UK funded project, Photonic Material Process for Data Storage, is underway. The aim of this project is to put in place a mechanism for continued business interaction between Seagate and Ilika. Also, the University of Southampton has been able to quickly demonstrate material properties and measurements in several areas that are of interest to Seagate. It is hoped that one of these areas can become the focus on a future Innovate UK funded project. The partners are actively working on this at the moment.
Impact Ellipsometry of 2D materials Improved annealing processes for 2D materials Processes for lower temperature deposition of 2D materials Invited to Participate Knowledge Transfer Network, UK led workshop: Contact: Monika Dunkel monika.dunkel@ktn-uk.org Participated in Flexible and Printed Electronics, Displays & Photonics demonstrator workshop, 21 November 2017, Cambridge
Start Year 2016
 
Description Invited to give a seminar talk in Saskatoon 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Gave a seminar talk at the University of Saskatchewan to fellow researchers and postgraduate students which opened up more avenues for collaboration.
Year(s) Of Engagement Activity 2018
 
Description Organised a symposium around Chalcogenide - 30 April - 3 May 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact ~45 fellow researchers and some people from industry attended the symposium to find out about the research that was taking place and create links with other organisations and industries.
Year(s) Of Engagement Activity 2018