Beyond Blue: New Horizons in Nitrides

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy

Abstract

Our research is based on gallium nitride and its alloys, an amazing family of materials which can emit light over a wide range of colours - from the infra-red (IR) to the ultra-violet (UV). Already these materials are widely used in light emitting devices that are part of our everyday lives, perhaps most commonly in blue light emitting diodes (LEDs) and laser diodes (LDs). The LDs are at the heart of the blu-ray HD-DVD player, whilst the blue LEDs are combined with phosphors that emit other colours of light to produce white light. Such white LEDs are now very common in bicycle lights, torches and back-lighting for displays on portable electronic devices from mobile phones to tablet computers.

Cambridge and Manchester have been collaborating on materials for blue LEDs for over ten years. Our research has led to step changes in the understanding of the basic materials science and physics of the light emitting materials leading to improved LED efficiency. Also we have pioneered lower cost methods for the growth of the gallium nitride crystals used in LEDs which have been commercialised, and are currently being exploited by a UK company, Plessey, who are fabricating these devices at their UK factory in Plymouth. Whilst we aim to continue to improve both the performance and cost of our blue LED technology in collaboration with our industrial partners, enabling new applications, e.g. in health care systems, we are now looking beyond the blue LED to other applications of gallium nitride such as devices that will emit light in the green and UV parts of the spectrum. Currently nitride devices emitting in the green and UV have much lower efficiencies than blue LEDs, and this limitation prevents the full exploitation of the nitrides across the whole spectrum. Applying the successful Cambridge-Manchester approach of understanding the basic science underlying the materials' properties, and using this to drive device development, we aim to produce green LEDs for application in displays and in high quality white lighting for homes and offices. Perhaps even more significantly, UV LEDs could be a low-energy way to purify drinking water, which could save millions of lives in the developing worlds, and we are considering innovative approaches to the development of these devices.

Looking beyond LEDs, we will carry out research on LDs and even single photon sources. These latter devices, which emit one -and only one - photon on demand, are an enabling technology for quantum cryptography and quantum computation. We are already world leaders in the design and fabrication of blue single photon sources. The horizons we wish to explore are not necessarily new colours but devices with astounding new capabilities, such as the emission of pairs of entangled photons. Entanglement - which Albert Einstein referred to as "spooky action at a distance" - is a peculiar phenomenon by which changes made to one of the entangled pair of particles affect the other, even if the two are many miles apart. Entanglement can be used to achieve totally secure transfer of information. Gallium nitride can also be used in electronic devices, and so another emerging research theme at Cambridge and Manchester is the development of nitride transistors which will reduce the energy wasted as heat in high power applications such as computer power supplies, motor drives or power inverters of photovoltaic systems.

Overall, our research has the potential to provide clean water for millions, vastly reduce energy consumption and greenhouse gas emissions and to enable totally secure communications but there are many new applications on the horizon for GaN, and we hope that this platform grant will help us to keep the UK at the forefront of this outstanding developing technology.

Publications

10 25 50
publication icon
Blenkhorn WE (2018) Resonant photoluminescence studies of carrier localisation in c-plane InGaN/GaN quantum well structures. in Journal of physics. Condensed matter : an Institute of Physics journal

 
Description Droop in the efficiency of Nitride LEDs is one of the factors limiting their widespread deployment. We have found that droop occurs in bothy polar and nonpolar quantum well yielding important information non the underlying physics. More recent work on droop has revealed the role of excited localised states.
Preliminary work on cubic GaN has shown great promise. We have been awarded a 3 year EPSRC grant to extend the work on cubic material
Exploitation Route This work will help with the understanding of efficiency droop in LEDs.
The development of cubic GaN could lead to a new generation of LED materials
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Energy

 
Description Several grant proposals were made to EPSRC, including two Program grant proposals, a proposal for an Industrial Hub and a responsive mode application. The latter was successful.
First Year Of Impact 2016
Sector Digital/Communication/Information Technologies (including Software),Electronics,Energy,Healthcare
Impact Types Societal

 
Description EPSRC Responsive mode
Amount £495,375 (GBP)
Funding ID EP/R010250/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 02/2018 
End 12/2020
 
Title Research data supporting "Local carrier recombination and associated dynamics in m-plane InGaN/GaN quantum wells probed by picosecond cathodoluminescence" 
Description Research data in support of the publication "Local carrier recombination and associated dynamics in m-plane InGaN/GaN quantum wells probed by picosecond cathodoluminescence". We have included the original data (tab-separated text files) as plotted for the quantum wells, measured by spatially- and time-resolved cathodoluminescence. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Description Collaboration with Tyndall Insitute 
Organisation University College Cork
Department Tyndall National Institute
Country Ireland 
Sector Academic/University 
PI Contribution Input to theory work done at Tyndall Institute
Collaborator Contribution Theoretical input to program
Impact Significant number of papers
Start Year 2009
 
Description Cubic GaN 
Organisation Anvil Semiconductors
Country United Kingdom 
Sector Private 
PI Contribution This work is part of a joint program of work between us, the University of Cambridge and Anvil Semiconductors
Collaborator Contribution Anvil Semiconductors provide the substrate materials for our program on cubic GaN
Impact EPSRC responsive mode grant proposal that commenced Feb 2018
Start Year 2016
 
Description Exhibit at Blue Dot 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Exhibit at Blue Dot of LED lighting science, Blue Dot is a major science festival held at Jodrell Bank.
Year(s) Of Engagement Activity 2016
 
Description University of the 3rd Age 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Talk to organisation that provides forum for people in retirement to hear about scientific developments
Year(s) Of Engagement Activity 2016