LED Lighting for the 21st Century
Lead Research Organisation:
University of Cambridge
Department Name: Materials Science & Metallurgy
Abstract
A major factor preventing the acceptance of LED lighting in our homes and offices is cost. The Cambridge part of this proposal focuses on reducing the cost by growing LED structures on silicon substrates which are much deeper than the sapphire substrates normally used. Our industrial partner, PhotonStar LED, plans to use ultra-thin flip-chip LEDs, which means that the substrate has to be removed. A major challenge is for Cambridge to incorporate a novel interlayer in the growth process which facilitates the removal of the substrate.Initially Cambridge will use sapphire substrates to test our ideas for interlayers. For example, it is proposed to grow n-GaN on sapphire, followed by an AlGaN interlayer, followed by further growth of n-GaN, and then multi-quantum-wells of InGaN/GaN. The plan is for the AlGaN interlayer to facilitate the removal of the sapphire substrate plus some of the n-GaN.Having developed a suitable interlayer for growth on sapphire we will then move to growth on silicon with an interlayer. Possible candidates are AlN or SiN. Because of the higher dislocation densities in growth on silicon we will need to introduce additional interlayers of other materials to reduce the dislocation density. We will then deliver to PhotonStar LED an ultra-thin, low-cost, GaN LED structure emitting at 450 nm.
Publications
Humphreys C
(2014)
How Cutting-Edge Atomic Resolution Microscopy Can Help to Solve Some of the World's Energy Problems
in Microscopy and Microanalysis
Humphreys C
(2010)
Looking Inside the Fascinating Nanoworld Controlling Light Emission from InGaN/GaN Quantum Well Devices
in Microscopy and Microanalysis
Holec D
(2009)
HANSIS software tool for the automated analysis of HOLZ lines.
in Ultramicroscopy
Holec D
(2011)
Towards predictive modeling of near-edge structures in electron energy-loss spectra of AlN-based ternary alloys
in Physical Review B
Hocker M
(2016)
Determination of axial and lateral exciton diffusion length in GaN by electron energy dependent cathodoluminescence
in Journal of Applied Physics
Hibberd M
(2016)
Dielectric response of wurtzite gallium nitride in the terahertz frequency range
in Solid State Communications
Hao R
(2010)
The effects of annealing on non-polar (1 1 2¯ 0) a-plane GaN films
in Journal of Crystal Growth
Han Y
(2016)
Toward defect-free semi-polar GaN templates on pre-structured sapphire Toward defect-free semi-polar GaN templates on pre-structured sapphire
in physica status solidi (b)
Han Y
(2015)
Origin of faceted surface hillocks on semi-polar ( 1 1 2 ¯ 2 ) GaN templates grown on pre-structured sapphire
in Journal of Crystal Growth
Hammersley S
(2016)
Effect of electron blocking layers on the conduction and valence band profiles of InGaN/GaN LEDs
in physica status solidi c
| Description | A major factor preventing the acceptance of LED lighting in our homes and offices is cost. Hence we focused on reducing the cost by growing LED structures on silicon substrates which are much cheaper than the sapphire substrates normally used. Our industrial partner, PhotonStar LED, planned to use ultra-thin flip-chip LEDs, which means that the substrate had to be removed. A major challenge was for us to incorporate a novel interlayer in the growth process which facilitated the removal of the substrate. Initially we used sapphire substrates to test our ideas for interlayers. For example, it was proposed to grow n-GaN on sapphire, followed by an AlGaN interlayer, followed by further growth of n-GaN, and then multi-quantum-wells of InGaN/GaN. The plan was for the AlGaN interlayer to facilitate the removal of the sapphire substrate plus some of the n-GaN. This was successful. Having developed a suitable interlayer for growth on sapphire we then moved to growth on silicon with an interlayer. Possible candidates were AlN or SiN. Because of the higher dislocation densities in growth on silicon we needed to introduce additional interlayers of other materials to reduce the dislocation density. We delivered to PhotonStar LED an ultra-thin, low-cost, GaN LED structure emitting at 450 nm. The above was successful. In particular we developed suitable interlayers for growth on both sapphire and silicon substrates and then for removal of these substrates. We also developed additional interlayers of other materials (SiN and AlN) to reduce the dislocation density. The work in this project also contributed towards the filing of a patent on dislocation reduction in GaN LEDs on Silicon. |
| Exploitation Route | The fiondings were taked forward and pur to use by PhotonStar LED. When we started this project in 2008, PhotonStar LED had 5 employees, 3 part-time. When this project ended, in 2010, it had over 90 employees. We do not claim credit for all of this! However, it is consistent with our successful project. |
| Sectors | Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology |
| URL | http://www.gan.msm.cam.ac.uk |
| Description | A major factor preventing the acceptance of LED lighting in our homes and offices is cost. Hence we focused on reducing the cost by growing LED structures on silicon substrates which are much cheaper than the sapphire substrates normally used. Our industrial partner, PhotonStar LED, planned to use ultra-thin flip-chip LEDs, which means that the substrate had to be removed. A major challenge was for us to incorporate a novel interlayer in the growth process which facilitated the removal of the substrate. Initially we used sapphire substrates to test our ideas for interlayers. For example, it was proposed to grow n-GaN on sapphire, followed by an AlGaN interlayer, followed by further growth of n-GaN, and then multi-quantum-wells of InGaN/GaN. The plan was for the AlGaN interlayer to facilitate the removal of the sapphire substrate plus some of the n-GaN. This was successful. Having developed a suitable interlayer for growth on sapphire we then moved to growth on silicon with an interlayer. Possible candidates were AlN or SiN. Because of the higher dislocation densities in growth on silicon we needed to introduce additional interlayers of other materials to reduce the dislocation density. We delivered to PhotonStar LED an ultra-thin, low-cost, GaN LED structure emitting at 450 nm. The above was successful. In particular we developed suitable interlayers for growth on both sapphire and silicon substrates and then for removal of these substrates. We also developed additional interlayers of other materials (SiN and AlN) to reduce the dislocation density. The work in this project also contributed towards the filing of a patent on dislocation reduction in GaN LEDs on Silicon. |
| First Year Of Impact | 2010 |
| Sector | Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology |
| Impact Types | Societal,Economic |
| Description | Science Policy (Round Table meetings at No. 10 and BIS) |
| Geographic Reach | National |
| Policy Influence Type | Participation in a guidance/advisory committee |
| Impact | Increased funding for materials research has resulted. This will have economic impacts and on the quality of life |
| Description | Nitrides for the 21st century (Platform Grant) |
| Amount | £826,500 (GBP) |
| Funding ID | EP/H019324/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 11/2009 |
| End | 10/2014 |
| Description | Programme Grant: Lighting the Future |
| Amount | £6,361,650 (GBP) |
| Funding ID | EP/I012591/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 12/2010 |
| End | 11/2015 |
| Description | Aixtron |
| Organisation | Aixtron Limited |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | We grew world class GaN device structures on our Aixtron reactor(s), thus increasing Aixtron sales. |
| Collaborator Contribution | They donated to us a senior scientist for 25% of his time. They provided free servicing and maintenance of our growth reactor. |
| Impact | Increased sales of Aixtron growth reactors. |
| Description | Forge Europa (International Headquarters |
| Organisation | Forge Europa |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | Expertise. Solving a major problem with the reliability of some Forge Europa LEDs |
| Collaborator Contribution | Advice. Testing. Market forecasts. |
| Impact | Improved reliability and lifetimes of Forge Europa LED based products. |
| Description | PhotonStar LED |
| Organisation | PhotonStar LED |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | This was a jointly funded project by the TSB and the EPSRC, with the EPSRC funding the Cambridge University part of the project and the TSB funding PhotonStar LED. We optimized GaN epitaxial growth on both sapphire and silicon using novel interlayers that enable rapid removal of the sapphire or silicon substrate. We also developed dislocation reduction techniques. This research was successful and we supplied ultra-thin device structures to PhotonStar LED |
| Collaborator Contribution | The main contribution was the staff time of Dr Majd Zoorob, the CTO of PhotonStar LED. He spend a lot of time working with us. This was valuable to us and we learned a lot from him. Photon Star were a partner in a 2016 application (unsuccessful) for a manufacturing hub in GaN. |
| Impact | We produced ultra-thin flip-chip LEDs using novel interlayers. Multi-disciplinary: Materials science, physics, chemistry, electronics |
| Start Year | 2008 |
| Title | SEMICONDUCTOR WAFER COMPRISING GALLIUM NITRIDE LAYER HAVING ONE OR MORE SILICON NITRIDE INTERLAYER THEREIN |
| Description | The present invention provides a semiconductor wafer comprising: a substrate layer; and a first GaN layer having one or more SiNx interlayers therein; and wherein in the first GaN layer at least one SiNx interlayer has GaN penetrated through one or more portions of said SiNx interlayer and preferably has a thickness of from 0.5 to 10nm. |
| IP Reference | WO2012066269 |
| Protection | Patent granted |
| Year Protection Granted | 2012 |
| Licensed | Yes |
| Impact | This patent was transferred to a Cambridge spin-out, CamGaN Ltd, for commercial exploitation of the technology described in the patent. CamGaN was later acquired by Plessey semiconductors in 2012. A portfolio of products based on the CamGaN technology has been launched by Plessey and has generated positive market feedback. |
| Description | BBC Breakfast TV and BBC Radio "You and Yours" |
| Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Public/other audiences |
| Results and Impact | Interview of Prof Humphreys on BBC Breakfast TV, and on the BBC Radio "You and Yours" on low-cost LEDS sparked a lot of discussions Increased public awareness of LEDs |
| Year(s) Of Engagement Activity | 2009 |
| Description | Big Bang Fair (London) |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | Yes |
| Geographic Reach | National |
| Primary Audience | Schools |
| Results and Impact | Encouraged school pupils to study science Schools reported increased interest in science and increased numbers studying science |
| Year(s) Of Engagement Activity | 2013,2014 |
| Description | Chelterham Science Festival |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | Yes |
| Geographic Reach | National |
| Primary Audience | Schools |
| Results and Impact | More school pupils studying science Schools reported greater interest in science. |
| Year(s) Of Engagement Activity | 2013,2014 |