Many congratulations to Helen who won the Second Prize in the IOP Student Research Communication Competition at the UK Semiconductors Conference held in Sheffield in July 2015. Well done!

Spark Zhang and researchers at Imperial College have been featured in the Journal of Physics “Labtalk” articles series for his contribution to the work on ScGaN. You can read the full article here.

Many congratulations to Rachel Oliver, who has have received a prestigious RAEng/Leverhulme Trust Senior Research Fellowship from the Royal Academy of Engineering to help support her career while she focuses solely on the development of new technologies. Rachel will be relieved of teaching and administrative duties for the 2015/16 academic year and will focus on understanding the dependence of optical properties on structure in non-polar InGaN quantum dots, with the aim of developing improved nitride single photon sources. More information about the award can be found here.

The group has a new web site with information on research themes, group members, news and events at the Cambridge Centre for Gallium Nitride.

The International Conference on Nitride Semiconductors was held in Beijing from 1st to 4th September 2015, and many members of the group attended. 

Click on the images below to see photos of the event and to view the poster presentations.

Many congratulations to Helen who won the Second Prize in the IOP Student Research Communication Competition at the UK Semiconductors Conference held in Sheffield in July 2015. Well done!  Click on Helen's Photo below to view her research profile.

Many congratulations to Chris who has won the runner-up prize in the 2015 IOM3 Materials Science and Technology Literature Review Prize competition. The review is available online or free to download here.

Click on Chris's photo to view his research profile.

Congratulations to Colin who was awarded Honorary Fellowship to the Royal Microscopical Society at the recent MMC 2015 Conference in Manchester in July.

Click on Colin's photo to view his research profile.

Welcome to the new students John Jarman and Lok Yi Lee, who will begin their PhD studies at the Cambridge Centre for Gallium Nitride. We wish them the best of luck in their work over the coming academic year.

Progress in the PowerGaN project has been highlighted in recent editions of Semiconductor Today magazine, with two articles describing the project's work on HEMT passivation and high frequency HEMTs on silicon.

Reduced gate leakage and current collapse in GaN HEMTs.

High-performance GaN on silicon HEMTs

The annual GaN Christmas Dinner was held at Peterhouse College on 17th December. Current and past members of the group met to celebrate, with a visit from Santa Claus!

Every Wednesday is Cake Day in the group, and we enjoyed a festive GaN fruit cake on the last Cake Day before the Christmas holidays.

The Cambridge Centre for Gallium Nitride held our annual Christmas dinner on 17th December at Peterhouse College. We wish you all a Merry Christmas and a Happy New Year.

Members of the group attended the UKNC's Connected Nation symposium at the British Library in London in December. The event focusses on research council funding of information and communications technology. The group presented experimental demonstrations, prototype devices, packaged products and information about nitride light-emitters. More information about the event can be found at the EPSRC's Connected Nation web pages.

The UKNC 2016 Winter Conference was held at Robinson College on 6th and 7th January with contributed talks and posters from all UK research groups studying nitride materials, and invited talks from international researchers.

Many congratulations to John Jarman from the Cambridge GaN group who won the UKNC Student Poster Prize for his work on non-polar quantum dots. More information about the programme can be found at the UKNC web site.

Congratulations to John who has won the Student Poster Prize at the 2016 UKNC Winter Meeting for his cathodoluminescence studies on non-polar quantum dots. Well done!

The group's recent award of an Innovate UK grant for continuing cubic nitride growth on silicon carbide substrates supplied by Anvil Semiconductors has been reported in EE Times. The full article can be accessed here.

The Cambridge Centre for Gallium Nitride will host two large events at the Department of Materials for the 2016 Cambridge Science Festival. These will be an interactive hands-on workshop for children between 4 and 7 years old, and a research talk ideal for older children and adults.

The programme of events in the Department of Materials Science is available as a downloadable pdf here and in the media section of the web site.

Lots and lots of light bulbs!

Saturday 19th March 2016, Goldsmiths' Lecture Theatre 2

Three bookable slots from 10.30 am, 11.30 am and 12.30 pm.

This workshop is aimed at school children in the early years foundation stage and key stage 1. The children will discuss with scientists where electricity comes from, generate their own electricity to light a light bulb and find out why some lights use less electricity than others. Together with the scientists the children will do experiments which show not only that some light bulbs waste energy, but where that wasted energy goes.

Out of the Blue: how gallium nitride improves your life

2 pm, Saturday 19th March 2016, University Sports Centre

This talk explores the many ways that this incredible material is used not just for environmentally-friendly lighting, but for water purification, data transmission, power devices, and even in medical research

More information is available here.

The group's recent grant awarded by Innovate UK in collaboration with Plessey and Anvil Semiconductors has been featured on the front cover of February's Semiconductor Today magazine. The cover shows the interior of one of the Aixtron CRIUS II-XL 7 x 6 inch MOCVD systems currently installed at Plessey for growth of GaN on silicon. The full article is below. 

Currently, we are in the process of installing two reactors (the Aixtron reactor that was installed temporarily in the Physics of Medicine building, and a new Veeco reactor) in our new lab at the Department of Materials Science and Metallurgy. Having both growth and characterisation facilities in the same building will certainly improve our efficiency. We expect that the reactors will be available again from the end of April 2016.

Thanks to all members of the group who contributed their time and effort to design experiments and to help with preparation for the 2016 Cambridge Science Festival. Your hard work helped to make it our biggest and most exciting public event ever.

We presented an interactive talk in the 400-capacity University Sports Centre, exploring how an LED works, how combinations  of different LEDs and phosphors allow high quality colour rendering, visible light communication, and the use of gallium nitride as a potential single photon source for quantum encryption.

We also put on a workshop for children between the ages of 4 and 7 years old, about electricity, conversion of muscle power or electrical power to light, and how incandescent and fluorescent light bulbs waste more energy than LEDs. Children also got to colour in their own convection-powered dragons to take home.

The Cambridge Science Festival is the largest free science festival in the UK, and the city of Cambridge receives around fifty thousand visitors over two weeks to attend talks, exhibitions and workshops for adults and children. To keep these events free, research groups rely on funding from research councils and industry, and many students pay for events from their own pockets. The Cambridge Centre for Gallium Nitride is grateful for funding for public engagement from the EPSRC through our Platform Grant, and to the Worshipful Company of Armourers and Brasiers.

The installation of the new Veeco Propel 8" MOCVD reactor begins today, with crates being unloaded and unpacked. The reactor is to join our Aixtron 6" reactor that is also being installed at the Department of Materials, after being temporarily housed in the Physics of Medicine. The new Veeco Propel reactor will allow us to expand our work on GaN-based power electronics and scale our current devices to 8" substrates. The main reactor vessel is currently being plumbed in.

David Wallis has been invited to give a talk at the GaN Marathon workshop on GaN technology at the end of April, where the University of Padova will present an honorary degree to the 2014 Physics Nobel Laureate, Hiro Amano, for his work on developing GaN-based blue LEDs. David will talk about our work on developing GaN on large-area silicon wafers, GaN for power devices, and our new work on cubic GaN.

Rachel Oliver's EPSRC-funded research on developing InGaN quantum dots for single photon sources has been highlighted in a Science and Engineering South interview. The project is in collaboration with Professor Robert Taylor at Oxford University, Plessey Semiconductors, and Toshiba, and aims to develop room-temperature single photon emission from nitride quantum dots for encryption and security applications.

As a part of our group's downloadable learning resources, Rachel Oliver presents the first of a series of Researcher Profiles, where team leaders, postdocs and students in our group talk about their everyday life in the lab, what they enjoy about their research, and how they got into a career in science

Rachel's profile, plus links to her web page and LinkedIn page, can be found here.

Professor Robert Taylor and University Research Fellow Josh Nunn, who are currently collaborating with Rachel Oliver in developing InGaN single photon sources, have produced a video and learning resource about encryption using single photons for the Oxford Sparks online science series.

The group was pleased to receive a visit from 2014 Nobel Laureate in Physics, Professor Hiroshi Amano, last week. We had many interesting discussions on LEDs, laser diodes, GaN-based transistors and RF devices.

The group welcomes new summer student, Nicolas Piot. Nicolas will be working on materials for single photon sources, and we wish him every success for his stay in Cambridge.

Rachel Oliver and a team of group members were invited to present a talk and a set of exciting demos to the students of Chesterton Community College's Science Club earlier this month. The team demonstrated how to communicate using light, which included a simple LiFi data circuit, a demo on optical fibre communication, and an experiment to demonstrate the use of single photon sources for quantum key distribution, but with tennis balls! Well done to all who took part!

Many happy returns to Sir Colin Humphreys who celebrated his 75th birthday on Tuesday. We celebrated with a cake, and a group picnic on Friday 27th May, featuring many hexagonal cakes! Click on Colin's birthday card to see some of the many past and present members of the group.

LEDs are well-known for revolutionising white lighting, but Lata will be giving a talk and a series of demos that highlight the other uses of LEDs, such as for communication, health, and medicine. Demonstrations will be recorded live and will be uploaded to the BBC online archive after the event. The Hay Festival is an annual literary festival held in Hay-on-Wye in Wales.

Professor Martin Dawson from the Unviersity of Strathclyde will give an invited talk at the annual Armourers and Brasiers Cambridge Forum on Tuesday 14th June. The talk will describe recent collaborative work on GaN/polymer, GaN/diamond and GaN/nanocomposite hybrid LEDs for high-bandwidth visible light communications. This research was carried out with funding from the EPSRC Programme Grant "Ultra-Parallel Visible Light Communications (UP-VLC)".

https://www.msm.cam.ac.uk/forum/ABC-Forum2016-programme-draft.pdf

Congratulations to Helen for getting her recent article onto the cover of Physica Status Solidi(b). The paper is about the properties InGaN nano-rings grown by modified droplet epitaxy, and can be viewed as June's Paper of the Month.

Many congratulations to An Bao, Thomas Choi and James Griffiths for reaching the fifth and final round of the McKinsey Venture Academy 2016, after beating almost 200 other teams. The team has been investigating the market for solar photovoltaic LEDs to benefit people living in off-grid areas, and those with only intermittent access to electricity. Fingers crossed for the final in London on 9th June!

The next stage in our Innovate UK Energy Catalyst project on fabrication of cubic LEDs has arrived, and we plan to grow cubic GaN structures on 6-inch 3C-SiC substrates on (100) silicon, supplied by Anvil. The image shows Anvil's Daniel Nilsson with a standard 4-inch substrate. Menno is holding a new 6-inch large-area wafer.

Congratulations to John who has passed his first year PhD probationary review, with his paper on the processing of InGaN-based quantum light sources.

Congratulations to Christopher Ren, who has been awarded an EPSRC Doctoral Training Prize, which will allow him to continue his exciting work on multi-microscopy of GaN-based devices for six months after he submits his PhD thesis. Chris's research interests can be found here.

As part of a recent visit to the Department of Materials Science and Metallurgy by Sixth Formers from The Knights' Templar School in Baldock, we gave an interactive presentation entitled "Communication using Light", which focused on new approaches which might be enabled by gallium nitride, including visible light communication or "LiFi". We had fun with lasers, tennis balls and other toys!

Recent collaborative work between Cambridge and Manchester on efficiency droop has been highilghted by journalist Mike Cooke in July's issue of Semiconductor Today, which can be read here.

Many congratulations to John Jarman and Lok Yi Lee, who have both passed their First Year PhD Probationary Review examinations, and will proceed with the second year of their PhD studies. Well done!

Congratulations to first year graduate student Lok Yi Lee who won second prize in the IOP Science Communication Competition at the recent UK Semiconductors meeting for her talk on means to overcome the Green Gap in LED emission efficiency.

Leak checking is complete on our Aixtron MOVPE growth system which is being recommissioned in a new purpose-built lab. Hopefully exciting new samples will be grown very soon!

Our recent collaborative paper with the University of Manchester on terahertz cyclotron resonance spectroscopy of AlGaN heterostructures is being highlighted by APL in their "Most Read Editors Picks". You can download the open access paper here, or read it as our Paper of the Month.

Many members of the Cambridge GaN group are currently at the IWN conference in Orlando. Bookmark this page for daily updates on posters and talks from our group and our collaborators!

Friday 7 Oct

After a week of talks and posters, group members relax at the conference dinner, with special guests from Walt Disney World in Orlando.

Thursday 6 Oct

The many posters presented on Wednesday from our group and collaborators are still on display; drop into the Ballroom on the Lobby Level to take a look at our recent research!

Wednesday 5 Oct

Today in IWN, Dr. Rachel Oliver will talk about the cutting-edge electron microscopy and tomography techniques used to study nitride-based microcavity structures. She'll be talking in the Camellia/Dogwood room at 8:00 am.

The group is presenting nine posters in today's session. If you are following us on LinkedIn for IWN updates, here is the list of the posters for today: PS2.05, PS2.90, PS2.93, PS2.117, PS2.143, PS2.166, PS2.167, PS2.168, PS2.169.

Also. H. Qian (C2.2.05) from Sheffield will talk about the work done in collaboration with our group on GaN-based vertical FET structure. Good luck everyone for a successful presentation!

Tuesday 4 Oct

At IWN today, make sure you catch invited talks by Prof. Colin Humphreys and Prof. Stefan Schulz in International North.

At 14:00 Prof. Humphreys will talk about the atomic structure of polar and non-polar InGaN quantum wells, which are revealed by combining different microscopy and spectroscopy methods.

Prof. Schulz will talk about the work being done in collaboration with Cambridge on InGaN at 08:30; Dr. Rachel Oliver will be the session chair.

Today, we have a total of eleven talks, including five from our collaborators. If you are at IWN and would like to catch up with our recent research, bookmark this page for speakers and talk IDs for today, and the remainder of IWN:

Markus Pristovsek (B1.2.03),

David Wallis (B1.2.05),

Lok Y. Lee (A2.3.06),

Colin Humphreys (D1.4.01),

Fabien Massabuau (D1.4.03),

Thomas Choi (F0.3.04),

Stefan Schulz (D1.2.01),

Danqing Wang (B1.3.05),

Kean B. Lee (C2.1.05),

Sheng Jiang (C2.1.07)

Syed Z. H. Zaidi (C0.3.04).

Monday 3 Oct

On the first day of the meeting, our group and collaborators are presenting eight posters. Also, Colin Humphreys will be chairing the session of materials characterisation (D1.1). If you are at IWN this week, don't forget to drop by at the following posters to learn more about our recent interesting research work!

PS1.45 Phase Purity Analysis of MOVPE-Grown Cubic GaN Epilayers -- S.-L. Sahonta & M. Frentrup et al.

PS1.100 Preventing Trench Defect Formation in InGaN Quantum Wells Using Hydrogen -- F.C.P. Massabuau et al.

PS1.101 Characterization of InGaN Quantum Well Interface by X-Ray Techniques -- F.C.P. Massabuau et al.

PS1.102 Impact of InGaN Composition on Carrier Localization at Dislocations -- F.C.P. Massabuau et al.

PS1.105 Investigation of Carrier Localization in InGaN/GaN Multiple Quantum Well Structures using Terahertz Spectroscopy -- A. Dunn et al.

PS1.106 Nanocathodoluminescence Reveals the Mitigation of the Stark Shift in InGaN Quantum Wells by Silicon Doping -- J. T. Griffiths et al.

PS1.138 Influence of Hexagonal Inclusions and Stacking Faults on the Photoluminescence Spectrum of Cubic GaN Grown via MOCVD upon Large Area 3C-SiC/Si Substrates -- S. A. Church et al.

PS1.154 Optimisation of GaN LEDs and the Reduction of Efficiency Droop Using Active Machine Learning -- Bertrand Rouet-Leduc et al.

The Festival of Ideas is hosting Dimension Leap, a photography exhibition at Anglia Ruskin University that features images of our growth reactor, substrates and characterisation equipment. Visit the Festival of Ideas web site, and the blog of artist Marina Velez, who has collaborated with Priti Gupta in the GaN group to explore Priti's research.

Members of the group have been participating in a number of outreach events this summer, including Soapbox Science in Cambridge city centre, running events for the Cambridge University Alumni Festival, and showing female sixth formers at the Robinson College Women in Science Festival how the Hanbury-Brown and Twiss experiment for the characterisation of single photon sources works (and coincidentally proving that tennis balls are particle-like in nature!).

Welcome to Peter Griffin who recently joined the GaN team as part of the joint UCL and Cambridge Doctoral Training Centre in integrated photonic and electronic systems.

He has written a research profile, detailing his experimental work on GaN, and described what it is like to work in the group. Best of luck to Peter in his new PhD studies. 

Welcome to Bonding Ding and Peter Griffin, two new students to the group who will begin their PhD studies with Rachel Oliver. Best of luck for the coming year!

A new research profile is available here for Markus Pristovsek. Markus has been a member of the group since March 2012 and his profile tells us about his role in the group and what he did to get there, as well as some insight to the future of GaN. Read the profile here!

December's paper of the month is live and available here. The work of James Griffiths' et al. looks at the electron damage caused during nano-cathodoluminescence on nitride optoelectronics.

You can see abstracts and links to all of our paper's of the month here.

There is a new researcher profile available from Dr. Ted Thrush here. Ted joined the group from Thomas Swan and has particular expertise on MOCVD growth (Metal Organic Chemical Vapour Deposition) and device characterisation.

You can browse our growing collection of researcher profiles here.

Congratulations to Lok Yi Lee who has been elected to the NanoDTC Associate studentship. Lok Yi had to summarise her research and how she would like to work with the NanoDTC in a presentation of just two minutes! Lok Yi will be writing bite-sized nano themed articles and interviewing researchers for the DTC and in return will receive a travel grant of £2500 for attending nano related conferences.

Lok Yi is a second year PhD student in the centre for Gallium Nitride. Find out more about her research here and connect with her on LinkedIn.

Merry Christmas to all our collaborators, friends and colleagues! The group celebrated with a christmas dinner with a special visit from father Christmas himself!

We'll be kicking off the new year with the UK Nitrides Consortium's winter conference in Oxford, hope to see some of you there.

Some people like cracker jokes!

Unwrapping our presents!

The UK Nitrides Consortium's winter Conference will be held in Oxford on the 5th and 6th January and the Cambridge GaN centre will be there in full force! We have several talks across both days and a number of posters. Here's a programme of what we and our collaborators will be presenting and when. For more information on the conference itself see the UKNC website.

Thursday 5th January

12.15-12.30

Microstructural analysis of E-mode InAlN/GaN high electron mobility transistor structures grown on silicon wafer by metal organic vapour phase epitaxy

 F. Tang¹, I. Guiney¹, J. Barnard¹, D. J. Wallis¹, C. J. Humphreys¹, R. A. Oliver¹, K. B. Lee², Z. Zaidi², P. A. Houston², T. Martin³, P. Bagot³ and M. Moody³

¹ Dept. of Materials Science and Metallurgy, University of Cambridge

² Dept. of Electronic and Electrical Engineering, University of Sheffield

³ Dept. of Materials, University of Oxford

13.45-14.00:

Design of Normally-off V-groove Vertical High Electron Mobility Transistors using (11-22) Semi-polar GaN

H. Qian¹, K. B. Lee¹, S. Hosseini Vajargah², S. V. Novikov³, I. Guiney², Z. H. Zaidi¹, S. Jiang¹, D. J. Wallis², C. T. Foxon³, C. J. Humphreys² and P. A. Houston¹

¹ Dept. of Electronic and Electrical Engineering, University of Sheffield

² Dept. of Material Science and Metallurgy, University of Cambridge

³ School of Physics and Astronomy, University of Nottingham

14.00-14.15

High Voltage All GaN Integrated Cascode Metal-Insulator-Semiconductor Heterostructure Field Effect Transistors

S. Jiang¹, K. B. Lee¹, P. F. Miaja², I. Guiney³, Z. H. Zaidi¹, H. Qian¹, D. J. Wallis³, A. J. Forsyth², C. J. Humphreys³ and P. A. Houston¹

¹ Dept. of Electronic and Electrical Engineering, University of Sheffield

² School of Electrical and Electronic Engineering, University of Manchester

³ Dept. of Materials Science and Metallurgy, University of Cambridge

15.15-15.30

The Mg acceptor in GaN: synonymity and the classical qubit

K.P. O’Donnell¹_, A.K. Singh¹, P.R. Edwards¹, K. Lorenz², M.J. Kappers³ and M. Boćkowsk⁴

¹SUPA Department of Physics, University of Strathclyde, Glasgow

²IST, Universidade de Lisboa, CTN, Estrada Nacional 102695-066 Bobadela LRS Portugal

³Department of Materials Science and Metallurgy, University of Cambridge

⁴Institute of High Pressure Physics PAS, Sokolowska 29/37, 01-142 Warsaw, Poland

16.45-17.00

Nanoporous distributed Bragg reflectors for optical microcavities in non-polar GaN

J.C. Jarman¹, T. Zhu¹, Y. Liu¹, T. Ding², R.V. Kumar¹ and R.A. Oliver¹

¹ Dept. of Materials Science and Metallurgy, University of Cambridge

² NanoPhotonics Centre, University of Cambridge

Friday 6th January

11.00-11.15

Nano-cathodoluminescence reveals the effect of electron damage on the optical properties of III-nitride optoelectronics and the damage threshold

J. T. Griffiths¹, S. Zhang¹, J. Lhuillier¹, D. Zhu¹, A. Howkins², I. Boyd², D. Stowe³, D. J. Wallis¹, C. J. Humphreys¹ and R. A. Oliver¹

¹ Dept. of Materials Science and Metallurgy, University of Cambridge

² Experimental Techniques Centre, Brunel University, Uxbridge

³ Gatan UK, Abingdon, Oxon

11.15-11. 30

Thermal Redistribution of Carriers Amongst Localised states in InGaN/GaN Quantum Wells Investigated Using Temperature Dependent Resonant Photoluminescence

S. Hammersley¹, D. Tanner^2,3, M.J. Kappers⁴, R.A. Oliver⁴, C.J. Humphreys⁴, S. Schulz² and P. Dawson¹

¹ School of Physics and Astronomy, Photon Science Institute, University of Manchester

² Photonics Theory Group, Tyndall National Institute, Cork, Ireland.

³ Dept. of Physics, University of Cork, Cork, Ireland.

⁴ Dept. of Materials Science and Metallurgy, University of Cambridge

11.30-11.45

Spectroscopic studies of defects in zincblende GaN films

S. A. Church¹, S. Hammersley¹, P. W. Mitchell¹, M. J. Kappers², S. L. Sahonta², M. Frentrup², D. Nilsson³, P. J. Ward³, L. J. Shaw³, D. J. Wallis², C. J. Humphreys², R. A. Oliver², D. J. Binks¹ and P. Dawson¹

¹ Photon Science Institute & School of Physics and Astronomy, University of Manchester.

² Dept. of Materials Science & Metallurgy, University of Cambridge.

³ Anvil Semiconductors Ltd, Cambridge.

11.45-12.00

Investigations into high energy emission band from InGaN/GaN quantum well structures observed under high excitation power densities

G. M. Christian¹, S. Hammersley¹, M. J. Kappers², C. J. Humphreys², R. A. Oliver², D. J. Binks¹, P. Dawson¹

¹ School of Physics and Astronomy, Photon Science Institute, University of Manchester,

² Dept. of Materials Science and Metallurgy, University of Cambridge

12.00-12.15

Nanoscopic insights into the effect of silicon on core-shell InGaN/GaN nanorods: luminescence, composition, and structure.

C. X. Ren, F. Tang, R. A. Oliver, T. Zhu

Dept. Materials Science and Metallurgy, University of Cambridge

16.15-16.30

Sub-Poissonian electroluminescence emission from highly polarised non-polar InGaN quantum dots

C. Kocher¹, T. Puchtler¹, J. C. Jarman², T. Zhu², R. A. Oliver², R. A. Taylor¹

¹ Dept. of Physics, University of Oxford

² Dept. of Material Science, University of Cambridge

16.30-16.45

Non-classical light generation beyond the 200 K thermoelectric barrier with a-plane InGaN quantum dots

T. Wang¹, T. J. Puchtler¹, T. Zhu², S. K. Patra^3,4, J. C. Jarman², L. P. Nuttall¹, S. Schulz³, R. A. Oliver² and R. A. Taylor¹

¹ Dept. of Physics, University of Oxford

² Dept. of Materials Science and Metallurgy, University of Cambridge

³ Tyndall National Institute, University College Cork, Cork, Ireland

⁴ Dept. of Electrical Engineering, University College Cork, Ireland

16.45-17.00

Ultra-fast, polarized, single-photon emission from m-plane InGaN quantum dots grown on GaN nanowires

T. J. Puchtler¹, T. Wang¹, C. X. Ren², R. A. Oliver², R. A. Taylor¹ and T. Zhu²

¹ Dept. of Physics, University of Oxford

² Dept. of Materials Science and Metallurgy, University of Cambridge

And Our Posters

An HBr/Ar atomic layer etch process for precision gate recess etching of GaN-based transistors

X. Li¹, K. Floros¹, S.-J. Cho¹, D. Hemakumara¹, I. Guiney², D. Moran¹, C. J. Humphreys² and I. G. Thayne¹

¹ University of Glasgow

² Dept. of Materials Science and Metallurgy, University of Cambridge

Surface preparation of free standing AlxGa1-xN (0001) layers grown by MBE using a highly efficient RF plasma source

P.-M. Coulon¹, S. Novikov², C. T. Foxon², A. Bao³, R. A. Oliver³, C. J. Humphreys³, D. Allsopp¹ and P. Shields¹

¹ Dept. Electrical & Electronic Engineering, University of Bath

² School of Physics and Astronomy, University of Nottingham

³ Dept. of Materials Science and Metallurgy, University of Cambridge

Effects of dislocations on the optical properties of blue and green InGaN/GaN Quantum Wells grown at different temperatures

B. Ding, F. C.-P. Massabuau, S.-L. Sahonta, M.J. Kappers, C.J. Humphreys, R. A. Oliver

Dept. of Materials Science and Metallurgy, University of Cambridge

Characterization of basal stacking faults of (11-22) GaN using X-ray diffraction

M. Pristovsek, M. Frentrup, T. Zhu, F. Tang, R. A. Oliver and C. J. Humphreys

Dept. of Materials Science and Metallurgy, University of Cambridge

Structural analysis of MOVPE-grown zincblende GaN

M. Frentrup, S.-L. Sahonta, M.J. Kappers, C.J. Humphreys and D.J. Wallis

Dept. of Materials Science and Metallurgy,University of Cambridge

January's paper of the month is live and available here. It showcases the latest work on single photon sources from nitride quantum dots with our collaborators in Oxford.

You can see abstracts and links to all of our paper's of the month here.

Last weekend, Rachel Oliver and Colin Humphreys appeared on "The Naked Scientists" radio show on BBC Radio Cambridgeshire. The show was broadcast live and is now available as a podcast here. The programme focussed on how LED technology made with GaN is transforming lighting applications across the board. Also featured are robotics to treat heart failure and an investigation into whether we really do eat spiders when we sleep!

February's paper of the month is live and available here. It shows the work of Fabien Massabuau et al. to characterise dislocations with multi-microscopy in order to explore carrier localisation in InGaN.

Read a general introduction to our multi-microscopy work here.

You can see abstracts and links to all of our paper's of the month here.

Colin Humphreys, the head of the centre, has added to our researcher profiles. Read about how the group was founded and how it has grown.

Our full selection of research profiles are available here.

Many congratulations to Chris Ren who passed his PhD Viva Voce examination on Friday of last week! To read a bit more about Chris' work see his profile here.

This evening is the Cambridge Region Young Persons' Lecture Competition of the Institute of Materials, Minerals and Mining and the GaN group is very well represented. We have three entrants giving talks across our work on GaN

Lok Yi Lee will be presenting her work on the cubic project: "Cubic zincblende gallium nitride for green-wavelength light emitting diodes"
 
John Jarman and Helen Springbett will give two talks on their contributions to our work on quantum light sources. John on: "Light Machinery: nanoscale engineering of materials for quantum light sources" and Helen on: "Single photon sources for quantum cryptography"

The talks will be given on the 23rd February from 18:30 in Goldsmith's 1 in the Materials Science and Metallurgy building. All are welcome!

For more information on the competition see the IOM3 website.

The centre has just begun an exciting new £4.3 million EPSRC funded project to develop GaN on diamond microwave devices. The aim is to use diamond layers as a heat spreading layer to allow high power radio and microwave devices for 5G and 6G communication systems. The project is a collaboration with Bristol, Glasgow, Cardiff and Birmingham.

See our project page and the project's press release for more information.

March's paper of the month is a review paper on defects in III-Notride microdisk cavities, studied for applications in LEDs and low-threshold lasers. It is now live and available here.

Access our paper of the month archive here.

The Cambridge Science Festival is almost here! From the 13th to the 26th March researchers all across the city will be opening their doors to the public to share and shout about the amazing work they're doing. From medicine to particle physics there will be events for all interests and all ages.

Of course, we are no exception! The Cambridge Centre for Gallium Nitride will once again be running workshops about our work, both on the 25th March, as well as a presentation on how light is used in imaging on the 26th March.

Credit: Jean-Jacques Milan

 In the morning we will be running a brilliant, interactive session for 4-7 year-olds about light. Lots and Lots of light bulbs! will be running at 10:00, 11:00 and 12:00. For more information and to book your place click here.

Credit: Jeff Keyzer

At 13:35, for older kids (12+) and grown-ups we will present a talk with demonstrations on how light is used to communicate. You will see how the oldest civilizations used light based communication, how today it is the corner stone of the internet and how it will revolutionise future communication. Click here for more info.

Both these workshops take place in Goldsmiths' 1 on the ground floor of the Materials Science and Metallurgy building, shown below. Post code: CB3 0FS

On the 26th March the GaN group will also be part of a collaborative presentation called Seeing the Invisible. This will explore how we can use light to see inside our bodies. The talk will be delivered at 11:30 and 14:00 at UTC Cambridge, Robinson Way, CB2 0SZ. No booking required, so be early to avoid dissapointment! This is part of the Rising Stars outreach programme and other parts of the programme will be presenting innovative science outreach at the same venue all day.

Congratulations to John Jarman who won second prize in the regional heat of the IOM3 lecture competition. John's talk: "Light Machinery: nanoscale engineering of materials for quantum light sources" was part of our work on quantum light sources.

Last weekend the centre ran a number of workshops and talks that showcased our work to all ages. See some of the pictures below:

Spinning worms, snakes and dragons test the heat from the different bulbs. (Credit: Lok Yi Lee)

Some of the older kids asked harder questions! (Credit: John Jarman)

An energetic evesdropper intercepts the quantum tennis ball communication. Demonstrating quantum cryptography systems we work on. (Credit: Lok Yi Lee)

Fabien explains how we can feel the wasted energy of an inefficient light bulb as heat. (Credit: John Jarman)

Priti in purple. Our communication with light talk featured lots of vibrant demos. (Credit: John Jarman)

John shows off the single photon sources he has made in the lab. Designed to be used for quantum cryptography. (Credit: Lok Yi Lee)

Fabien was never short of volunteers! (Credit: Lok Yi Lee)

The Lots and Lots of Lightbulbs team, happy after running three sold-out sessions for 4-8 year olds. (Credit: John Jarman)

The journal Europhysics letters (EPL) has published its highlights of 2016, bringing to attention our review paper on Nitride quantum light sources. The paper by Tongtong Zhu and Rachel Oliver was selected under the Applied and Interdisciplnary topics category.

Helen Springbett is to start a summer Fellowship at the University of Tokyo through the Japan Society for the Promotion of Science. She will be working on characterisation of quantum dots using photoluminescence with Prof. Mark Holmes and Prof. Yasuhiko Arakawa at the Institute for Nano Quantum Information Electronics.

Raymond Smith will be joining the centre for a summer placement as part of his MRes within the IPES CDT programme. He will be working with Peter Griffin on exploiting the genetic algorithm for optimising porous GaN devices.

Before applying to the CDT Raymond studied natural sciences here at Cambridge.

Lok Yi has been selected as one of the finalists of the 2017 Materials Science and Technology Literature Review Prize of the Institute of Materials, Minerals and Mining, for her review ‘Cubic zincblende gallium nitride for green-wavelength light emitting diodes’. She will take part in a masterclass event on 26th June at the Institute of Materials, Mineral and Mining in London. 

Read more about the competition here.

Congratulations to Bertrand Rouet-Leduc who passed his PhD viva last week! He convinced his examiners in just 90 minutes and has minor corrections. His project in the Cambridge Centre for Gallium Nitride concerned modelling of the efficiency of GaN based LEDs using machine learning techniques. He has also applied the same techniques to earthquake prediction and is continuing this work with a felowship at Los Alamos National Laboratory.

Read more on his work on his researchgate profile.

Congratulations to John Jarman who won a prize for his poster presentation in the Department of Materials Science and Metallurgy's annual showcase of graduate student work. His poster presented his work on nanopillars towards GaN based single photon sources.

Read more about the single photon source project and see John's profile for more information.

Dr Rachel Oliver and Dr Tongtong Zhu have been recently awarded an EPSRC Impact Acceleration Account Follow-On Fund on porous GaN technology.

We have recently taken our newly developed workshop on colour to two Cambridgeshire Primary Schools, Fen Drayton and Fawcett Primary in Trumpington. As you can see we all had a lot of fun!

Crazy About Colour teaches children about the nature of colour and light. We saw how white light can be split up to make a rainbow and how dark inks are made up of several different colours, which can be separated to make chromatography butterflies.

We are in the process of developing some of our workshops (including this one) into downloadable resources. If you would like to be kept informed on this or other aspects of our science outreach work please email gan-schools@msm.cam.ac.uk.

Fen Drayton showing off their chromatography Butterflies

Rachel meets some special guests.

Chromatography butterflies undergoing metamorphosis.

Some tidying up to do!

Lots to hear from the GaN group today at ICNS including Rachel Oliver's invited talk "Advanced microscopy of InGaN/GaN heterostructures" kicking off straight after lunch (A9.1). Before that is a talk from our collaboration with Robert Taylor's group in Oxford "Highly polarised electrically driven single photon emission from a non-polar InGaN quantum dot" given by Claudius Kocher (B8.4). We're well represented in this evening's poster sessions too: A2.4, C02.8, C02.18 and C02.45. Everything from X-ray characterisation of stacking faults(A2.4) to design of all GaN cascodes(C02.45). 

Follow all our updates here.

General Conference information here.

Our full complement of summer students has at last been assembled. From left to right they are:

• Oliver Tesh who's working on modelling LED efficiency with David Wallis.
• Pat Wichitwechkarn who's developing hybrid materials using porous GaN structures with Peter Griffin.
• James Moloney who's developing an educational android app under Fabien Massabuau.
• Raymond Smith who's an MRes student as part of the IPES CDT and is working on optimising porosity of GaN using a genetic algorithm with Peter Griffin.

If you're interested in working with the centre then let us know! We're very pleased to host a variety of projects for 6th form students, undergraduates or above.

Rachel Oliver is helping organise an exciting meeting at the Institute of Physics next month, along with collaborators from the University of Oxford and the University of Bath. 

The title is "Quantum Light-Matter Interactions in Solids: towards integrated quantum photonics" and it will be held at the Institute of Physics in London between the 7th and 8th September.

The abstract deadline has just been extended to 28th August, so there is still time to submit an abstract to come and contribute!

Apply or read more here.

Our latest paper of the month showcases the work of Bertrand Rouet-Leduc on applying machine learning methods to optoelectronic simulations. Read the paper here.

Access our paper of the month archive here.

Our new atomic force microscope is now fully operational. The new microscope is a Bruker Dimension Icon Pro and upgrades our scanning probe capability to allow:

• Automated mapping of samples up to 8 inches in diameter.
• Peak force capability.
• Additional conductivity and photo-conductivity measurement techniques.

This Bruker AFM has been funded by the Sir Henry Royce Institute, and we will be managing it as a facility for users from across the Institute as well as using it for our own research.

Fabien Massabuau's article in the Journal of Applied Physics has made their list of most read articles of 2017. The article, "Carrier localization in the vicinity of dislocations in InGaN" comes out of our work on multi microscopy techniques.

You can read it here for free for a limited time.

The centre is looking for a new post-doctoral research position to work on the growth of GaN on Si HEMT structures in collaboration with the Universities of Cardiff, Sheffield, Glasgow and Manchester and aims to demonstrate an integrated GaN technology which delivers both RF power amplifiers and power switches in a single circuit.

For more info and to apply click here.

Prof. Sir Colin Humphreys from the Cambridge Centre for Gallium Nitride was presented with the Henry Clifton Sorby Award, the highest award of the International Metallographic Society (IMS) and ASM International, last week at the Materials Science and Technology 2017 Meeting in Pittsburgh, USA.

He was awarded in recognition to his lifetime achievement in the field of metallurgy. Read more about the award and why Colin was honoured with it here.

Congratulations to our very own John Jarman for second place in the department's image competition for his image of GaN facets revealed by KOH etching.

You can see some of the other winners in the department's twitter feed.

We're very pleased to have three short term students working with us over the course of this academic year. Two are final year undergraduates in the department undertaking their part III projects, Oliver Tesh and Thomas Weatherley. Thomas will be obtaining photoconductive atomic force microscope data as part of his project using a capability recently made available to the group through the Sir Henry Royce Institute.

Oliver Tesh in the X-Ray Diffraction Laboratory

Domenic Peake studying Feynmann (As new students ought).

Welcome also to Domenic Peake who is spending some of his gap year to work with us to develop our educational LED apps.

We're always on the look out for enthusiastic young scientists who want to contribute to our work, so please do get in touch!

Peter Griffin will be competing in the regional heats of the Institute of Physics' 3 minute wonder competition. He won't tell us much except it might involve a sponge cake....

You can go and hear him and the other competitors at 18:30 on the 29th November at the IOP in London. Full details here.

The image shows an 8" GaN-on-Si wafer from our Veeco large wafer reactor being imaged on the 8" stage of our new Bruker Nano Surfaces Dimension Icon Pro AFM.  We even have automated mapping capability to efficiently sample morphologies and materials properties across the wafer! This is an exciting development for the production of GaN devices.

The AFM is part of the Cambridge spoke of the Sir Henry Royce Institute. Read more about how we use it here.

Our fourth year undergraduate student Thomas Weatherley attended his first academic conference last week at the winter meeting of the UK Nitrides Consortium (UKNC) and came away with the student poster prize.

The poster shows his work with the group, in which he is exploring the photoconductive AFM capabilities of our new Veeco Dimension Pro AFM. 

We were pleased to hear that Domenic Peake, who has been working on developments of our educational GaN Lab App during his gap year, has been given an unconditional offer to study physics at Oriel college Oxford.

Congratulations to Domenic and to Oriel college. He will be a great asset!

We look forward to welcoming Domenic back for a few months in April before he moves to the City of Dreaming Spires.

Recent work performed in collaboration with researchers at the university of Bath has been reported on by Semiconductor Today. The work, in the Journal of Applied Physics, reinterprets the ABC model of carrier distribution suggesting it is more uniform than previously thought. Read their article here.

As Colin approaches his retirement medium.com have a wonderful article of his life from upbringing in Luton through founding this centre to now, with some wonderful stories along the way. Wel worth a read here.

We are pleased to welcome Petr Vasek to the group for 6 months. Petr is visiting from Brno in the Czech republic and will be working on characterisation for studying nucleation and defect formation processes in zincblende GaN films. You can read more about our work on cubic GaN here.

Love is in the air in the GaN centre, and we're celebrating with a beautiful heart shaped cake from our lovely cleaner Linda, only her second foray into baking. It will certainly be enjoyed wholeheartedly.

Rachel has been nominated to give the Rank Prize Lecture at the IOP's Photon 2018 at the beginning of September. The nomination was awarded in consultation with the organisers of Photon 18 and the trustees and members of the rank prize fund's optoelectronics committee and includes a cash prize.

Congratulations Rachel! We look forward to hearing your lecture.

Why are the Rank prizes awarded for nutrition and optoelectronics? Read the story of their founder here.

The GaN group has been really busy with outreach recently. We visited year 2 classes at both the Grove primary school and the Stephen Perse Pre-prep where we learnt all about colour and light and made chromatography butterflies.

Children at the Grove told us:

"I was surprised when the brown ink changed to lots of different colours and not brown!"

How does the ink do that?!?

"I liked when the torch was shining different colours of light and how that made lots of different, pretty colours."

"I was interested when we dipped the ink because it got all soggy but, at the end, the colours changed."

Children at the Stephen Perse pre-prep show off their chromatography butterflies

Later in the week we had an exciting visit to the lab from 3rd Trumpington Brownies. The Brownies learned all about material science and crystals through building crystal models, examining salt crystals with microscopes and were introduced to our cutting edge electron microscopy and atomic force microscopy.

If you would like support for an education project then please get in touch.

Dr Rachel Oliver will be appearing on "The Naked Scientists" Radio Show on BBC Radio Cambridgeshire at 6 pm on Sunday (25^th March). She will be answering listeners' questions on the theme of materials science. If you want to listen in, you can do so here:

http://www.bbc.co.uk/programmes/p060vvsp 

On Saturday 24th March, the Cambridge Centre for Gallium Nitride joined many other scientists on the West Cambridge site in introducing our research to the general public.  This year, we chose microscopy as the theme of our public lecture with Rachel Oliver and Lok Yi delivering a talk called "The atomic gramophone and other stories" which explained the limitations of light microscopy and the new opportunities offered by electron microscopy and atomic force microscopy. After the lecture, we set up a drop in workshop in the common room at the Department of Materials Science and Metallurgy, explaining LED light bulbs to visitors with the help of our interactive Android app.

The Cambridge Centre for GaN is delighted to be part of an ambitious new EPSRC-funded research project led by the University of Glasgow which aims to develop novel manufacturing techniques for advanced materials and devices. 

The ‘Hetero-print’ project brings together chemists, physicists, materials scientists and engineers from the Universities of Cambridge, Glasgow, Manchester, Sheffield and Strathclyde.

Over the next five years, they will use a £5.54m Programme Grant from the EPSRC to develop a range of new techniques and applications for printing of devices on the micro and nanoscales. The Hetero-print team will work to extend the existing capabilities of micro and nanoscale transfer printing, a technique which allows the manufacture of high-quality, high-performance electronic devices. In recent years, it has enabled the development of complex technology such as flexible displays made from micro-LEDs. 

Currently, transfer printing uses a high-precision mechanical pick-and-place assembly technique which exploits the adhesive properties of soft polymer stamps. The Hetero-print team will investigate for the first time the potential of transfer printing to create highly integrated systems made from both organic and inorganic materials, as well as smart active stamp technologies, which could bring new capabilities to the manufacture of electronic, photonic and other micro-systems. This approach has been identified as a major new direction for electronics manufacturing.

For more information please see the full press release here:  https://www.gla.ac.uk/news/headline_578516_en.html 

Dr. Fabien Massabuau has been awarded the Armourers and Brasiers' Post-doctoral Prize 2018 for his excellent contribution to research and teaching in the Department of Materials Science & Metallurgy.

Dr James Griffiths has finished his work in our group and started his new job in a relevant company. He has contributed greatly to the research in this group and we sincerely appreciate his effort. The capability, insight and intelligence he has shown in the group will certainly assist him to a successful career in the future.

Meanwhile, we are excited to welcome a new master's student to the group, Naomi Vargha. She will be working on the characterisation of boron nitrite. Naomi joins us from France and will undertake a three-month internship in the group. We hope that she will enjoy the UK and the research in Cambridge.