Nitrides for the 21st century

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy


Our research has the potential to save millions of lives, save energy, save carbon emissions and enable totally secure communications. It is based on gallium nitride, which is probably the most important new semiconductor since silicon. Unlike silicon, gallium nitride emits brilliant light when a small electric current is passed through it. We can produce light of any colour (for example blue, green, yellow, red) by adding more and more indium to gallium nitride. On the other hand, if we add aluminium to gallium nitride we can produce ultra-violet light. Gallium nitride based light emitting diodes (LEDs) and laser diodes are already in widespread use, for example as LED traffic lights and as Blu-ray laser diodes for the latest DVD players. If we coat a blue LED with a yellow-emitting phosphor then a cool white light is produced, and such white LEDs are used as front bicycle lights, flashlights, backlighting for mobile phones, etc,The aim of this Platform Grant is to underpin our research in a number of key areas. Gallium nitride produces light so efficiently that if we could use white gallium nitride based LEDs for home and office lighting we could save 15% of all electricity used, reduce carbon emissions from power stations by 15% and close eight large power stations. However, high-power white LEDs are too expensive for home and office lighting, and the quality of the white light is too poor to be acceptable. Gallium nitride based LEDs are currently grown on two-inch diameter sapphire wafers. We are developing their growth on six-inch silicon wafers. If successful, this will reduce the cost of each LED by a factor of ten, which will make white LEDs cheap enough for home and office lighting. Some challenging new science in required for this, but we are world leading in this research. We are also planning to produce high quality white light, like natural sunlight, by developing new green and red phosphors, and we will tailor the wavelength of our LEDs to maximise the excitation of these new phosphors. We also plan to eliminate phosphors totally, which will further improve the efficiency, and produce white light by mixing blue, green, yellow and red LEDs. Currently green and yellow LEDs have relatively poor efficiency, for reasons which are not totally clear, and we plan to solve this problem. Solving both the problems of cost and quality will yield low-cost high-efficiency high-quality lighting for our homes and offices, with the substantial energy and carbon savings referred to above.Deep ultra-violet radiation stops bacteria and viruses from reproducing and hence essentially kills them. Aluminium gallium nitride LEDs at present emit in the deep-UV, but their efficiency is too low to be useful. We propose to make highly-efficient LEDs emitting in the deep-UV. These could be used to purify drinking water in the developing world. Over one billion people in the world do not have access to drinkable water, and drinking impure water kills more people in the world than AIDS. Our research could lead to literally millions of lives being saved. The LEDs operate at typically 4 Volts and so can be powered by solar cells, ideal for the developing world. Additionally such deep-UV LEDs could be used in a flashlight to shine on hospital walls, floors and bedding to kill superbugs.We plan to develop a novel gallium nitride based light source called a single photon emitter, which emits a single photon on demand. This would be used for sending totally secure messages. For example a mobile phone, with a single photon emitter, could send a message to a cash machine for you to obtain money, with no possibility of anyone obtaining your bank details, PIN number, etc. Our research therefore promises substantial benefits to the health, wealth, wellbeing and security of our society.

Planned Impact

As agreed with EPSRC Impact Summary is not required


10 25 50

Description We have developed a new low-cost way of growing gallium nitride on 6-inch diameter silicon which will substantially reduce the cost of energy-efficient LED lighting. This was highlighted by the then science minister, David Willetts, in his report "Eight Great Technologies", published in 2013. We filed two patents on our work, in 2011 and in 2013 . Both have been granted. The UK company Plessey acquired our technology in 2012 and are now manufacturing such GaN LEDs, based on our technology, at their factory in Plymouth. This is the first ever manufacturing of GaN LEDs in the UK and the first commercially available GaN LEDs on silicon in the world. In 2014, Plessey sold over 2 million LEDs based on our technology. All other commercial white LEDs are grown on small-diameter sapphire or SiC substrates, which are expensive. Our low-cost high-efficient LEDs grown on large-area (150 mm diameter) silicon should enable their widespread use in home and office lighting, which will save the UK 10% of electricity, a saving of £2 billion per year. It will also save 10% of carbon emissions from power stations. In September 2015, Plessey raised £30 million from the Deutsche Bank and £30 million from other investors to enable them to expand their production. They are currently employing over 100 people in Plymouth manufacturing our LEDs. So our EPSRC funded research is generating manufacturing jobs and wealth in the UK.
Our research has had impact across the LED supply chain. We have helped Aixtron (factories in the UK and Germany) to sell their growth reactors by advising them on their future requirements. We helped the UK SME Forge Europa (manufacturing in Ulverston, Cumbria) to solve a major problem they were having with the reliability of some LEDs which were being incorporated into their products. February 2019 addition. Plessey continue to manufacture LEDs in Plymouth, Devon. Their latest products, launched in 2018, are microLEDs. Each microLED is as small as 1 micron. This is the smallest in the world. This world-leading product is based on the GaN-on-Silicon technology developed in this grant, which Plessey acquired. It gives Plessey a competitive advantage in microLEDs. Such microLEDs are exceptionally bright and may be used in next-generation smart watches, smart phones, TVs, etc. A display screen made from microLEDs is visible in bright sunlight. March 2020 addition. Plessey has made significant advances with its microLEDs based on the GaN-on-silicon technology developed on this grant. Last year it had achieved blue and green emission. In the last 12 months it has achieved red emission. These are the world's first GaN-on-silicon red LEDs, and Plessey issued a press release in December 2019 about this. So Plessey now has blue, green and red micro LEDs for displays. This is a disruptive, game-changing technology for the next generation of Augmented Reality (AR) head-mounted displays, sports watches, mobile phone screens, etc. The displays are so bright they can be seen in bright sunlight, and their power consumption is very low. They are poised to replace LCD and OLED displays, since they are much brighter and have lower power consumption. In 2019, Plessey partnered with Vuzix, a leading supplier of smart glasses and AR, and Plessey is now licencing the technology to partners to manufacture on a commercial scale, to make a mass market product. This is all based on the work funded through this award.
Exploitation Route The UK company Plessey has already commercialized our research, as outlined above. Aixtron (UK and Germany) have already acknowledged our help to them in achieving many £millions of sales. Forge Europa (Cumbria) acknowledges our help in solving a major LED reliability problem they had. See above. Humphreys spun-out two companies, CamGaN and Intellec, to exploit the GaN-on-silicon LEDs developed on this grant. These companies were then acquired by Plessey, which manufactured these LEDs and now microLEDs based on our technology. Plessey is manufacturing in the UK, in Plymouth.
Sectors Aerospace, Defence and Marine,Chemicals,Construction,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Healthcare,Leisure Activities, including Sports, Recreation and Tourism,Manufacturing, including Industrial Biotechology,Transport

Description The overall economic and societal impact of the research has been substantial. First, there is the direct exploitation of our research in the UK by Plessey. This is detailed below in the "Key Findings" section. Let me give some additional information. One of the PDRAs employed on this grant, David Wallis, led a team of three of my PDRAs (Plessey employed them all) in transferring to Plessey in 2012 the GaN LEDs on large area Silicon technology developed on this grant and on earlier EPSRC grants. This team of three of my PDRAs transferred this technology from my university GaN growth system to the Plessey commercial-scale growth system in only eight weeks (we had been told that it would take at least two years!). This has resulted in the world first of Plessey being the first company in the world to have GaN-on-Si LEDs commercially available, in 2013. In 2014 they sold over 2 million such LEDs. They are employing over 100 people to do this in the unemployment blackspot of Plymouth. I believe this is a great good news story for the EPSRC! We have also substantially helped the company Aixtron to increase its sales and Forge Europa to solve a key LED reliability problem, as mentioned in the "Key Findings" section below. We have performed all this exploitation work while performing world-class basic research on GaN based materials and devices, as evidenced by our large number of well-cited publications and also invited talks at international conferences. Second, we have spent a huge amount of time promoting the importance of GaN LEDs for saving energy and carbon emissions. We have given public lectures, schools talks, advised local councils, had meetings at BIS, spoken many times with the then Science Minister, David Willetts, and had two meetings with the then Prime Minister, David Cameron at Number 10. We believe that this has all helped the UK to start to change its lighting in homes, offices and streets to LED lighting. This change is accelerating and in the next 5-10 years I confidently expect GaN LED lighting to become the dominant form of lighting in the UK. When this happens, the UK will save 10% of all electricity use, 10% of carbon emissions from power stations and over £2 billion per year in electricity costs. In addition, we would not need to build about 10 new power stations. Consumers fitting LED lighting will save on their electricity bills, and save on replacing light bulbs because LEDs are so long lasting. LED lighting is increasingly being used in all new buildings because of the energy savings. Hence the construction industry is also being influenced. These are major economic and societal benefits that our EPSRC-funded research has helped to enable. February 2019 update. I believe it is now totally clear that GaN LED lighting will become the dominant form of home and office lighting in the world. For example, many supermarkets only sell LED light bulbs, all of them are made from GaN. Plessey continues to manufacture LEDs in the UK, at Plymouth, its latest products being microLEDs, based on our GaN-on-silicon technology, which are world leading (see below). Plessey sells LED chips to other companies to use in light bulbs, etc., and they are used in many sectors, listed below. A few months before the end of this grant Humphreys started discussions with an Indian student, Priti Gupta, about coming to Cambridge to work on GaN/graphene devices. Further information will be given in my report on the next grant, Lighting the Future. March 2020 update. MicroLEDs are a fast-emerging display technology because they are extremely bright and can be seen bright daylight, a problem with existing displays in sports watches and mobile phone screens. Existing microLEDs use a pick-and-place technology in which individual microLEDs are assembled into a display one-by-one. This slow process is not viable for manufacturing. The Plessey process, based on the GaN-on-silicon LEDs developed on this grant, overcomes this problem by using monolithic microLED multiple emitters on a single chip. This is the only monolithic microLED solution in the world, and it is based on the science and technology funded on this EPSRC grant. In the last 12 months Plessey have partnered with other companies to make a mass-market product. The date our GaN-on-silicon LEDs were first manufactured by Plessey was in 2014, as given below. The date the microLEDs were first materialised was 2019/2020.
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Chemicals,Construction,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Leisure Activities, including Sports, Recreation and Tourism,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections,Retail,Transport
Impact Types Societal,Economic

Description Science Policy (Round Table meetings at No. 10 and BIS)
Geographic Reach National 
Policy Influence Type Participation in advisory committee
Impact Increased funding for materials research has resulted. This will have economic impacts and on the quality of life
Description Beyond Blue:New Horizons in Nitrides (Platform Grant Renewal)
Amount £979,288 (GBP)
Funding ID EP/M010627/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2015 
End 01/2020
Description Free-standing wurtzite AlGaN substrates for DUV devices
Amount £688,438 (GBP)
Funding ID EP/K008323/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2013 
End 01/2017
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 Sharp Laboratories Of Europe Ltd
Amount £27,000 (GBP)
Funding ID RG50526 
Organisation Sharp Laboratories of Europe Ltd 
Sector Private
Country United Kingdom
Start 11/2006 
End 09/2010
Description Silicon compatible GaN Power Electronics (Programme Grant)
Amount £6,196,718 (GBP)
Funding ID EP/K014471/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2013 
End 02/2018
Description Study of semi-polar and non-polar nitride based structures
Amount £560,766 (GBP)
Funding ID EP/J003603/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2012 
End 12/2014
Title GaN LEDs on silicon 
Description This is a new low-cost method for growing GaN LEDs 
Type Of Material Improvements to research infrastructure 
Year Produced 2012 
Provided To Others? Yes  
Impact Plessey is manufacturing LEDs in the UK based on our technology 
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 Plessey collaboration 
Organisation Plessey Semiconductors Ltd
Country United Kingdom 
Sector Private 
PI Contribution We developed a new low-cost high-efficiency method for making GaN LEDs. we set up two companies which Plessey acquired. Plessey also hired 3 of my post-docs to transfer the technology and as permanent hirings. We continue to collaborate with Plessey, providing them with advice. We also provided them with two growers for a period of three months when their main grower left in 2016.
Collaborator Contribution Plessey process LED structures that we grow and we exchange information. The processing of our wafers is very important for our research.
Impact Plessey are manufacturing GaN-on-Si LEDs at Plymouth based on our technology. This is the first and only manufacturing of GaN LEDs in the UK. Plessey had the first commercially available GaN LEDs on large area Si in the world, based on our Cambridge technology, funded by the EPSRC. Plessey raised £30 million from the Deutsche Bank and £30 million from other investors in 2015 to expand their GaN-on-Si LED manufacturing. The are employing over 100 people in Plymouth in LED manufacturing. They are manufacturing millions of LEDs per year. Materials Science, Physics, Chemistry, Electronics.
Start Year 2010
Description Thomas Swan Scientific Equipment Ltd 
Organisation Thomas Swan and Co Ltd
Country United Kingdom 
Sector Private 
PI Contribution The collaboration ceased when Thomas Swan Scientific Equipment was taken over by Aixtron, and we then collaborated with Aixtron.
Collaborator Contribution Thomas Swan donated us a growth reactor in 2000.
Impact Many publications which showed the excellence of the Thomas Swan growth reactor.
Title GaN on Si device substrate with GaN layer including sub-10nm SiNx interlayers that promote crystal growth with reduced threading dislocations 
Description The present invention relates to a semiconductor material and the use of a semiconductor material in wafer form as a support for forming a light emitting diode (LED) or other optoelectronic device. Further, the present invention relates to a method of constructing high quality optoelectronic devices using the wafer. In particular, the present invention relates to an improved LED having a silicon substrate that minimises the dislocation-defects that occur when larger support wafers are used. A gallium nitride (GaN) semiconductor substrate for grown of nitride semiconductor devices comprises an underlying wafer that carries a first GaN layer that has one or more very thin silicon nitride SiNx inter-layers therein. These Si N x inter-layer(s) are 0.5nm to 10nm thick and the GaN penetrates through one or more portions of the inter-layer preferably to form discrete crystalline structures (3D GaN). Preferably these crystalline structures help reduce threading dislocations when the GaN layer is grown, by MOVPE for example. Additionally, below the GaN layer, an aluminium nitride AlN nucleation layer may lie on the underlying wafer with an aluminium gallium nitride AlGaN buffer layer above the AlN and below the GaN layer. The underlying wafer may be silicon Si.; The AlGaN layer may have a graded alloy content so the amount of aluminium decreases from the Si wafer towards the GaN layer. The GaN layer may be undoped and a second, doped, GaN layer may be formed on top, the dopant concentration of Si or Ge increasing with increasing distance from the first undoped GaN layer. Devices may be formed including MQW structures which may comprise LED or Solar (photovoltaic) devices. The substrate may be from 6 inches (15cm) to 12 inches (30cm) in diameter. 
IP Reference WO2012066269 
Protection Patent granted
Year Protection Granted 2010
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 The present invention relates to a semiconductor wafer comprising: a substrate; a first AlGaN layer on the substrate; a second AlGaN layer on the first AlGaN layer; a Ga N layer on the second AlGaN layer; and a plurality of crystalline GaN islands between the first and second AlGaN layers. 
IP Reference WO2014053831 
Protection Patent application published
Year Protection Granted 2012
Licensed Commercial In Confidence
Impact This development will reinforce the GaN-on-Si technology developed in Cambridge centre for GaN, which provides an alternative way to achieve high performance GaN-on-Si LEDs. Commercial exploitation of this discovery is under discussion.
Company Name CamGaN 
Description Set up to exploit GAN LEDs on 6 inch Silicon. 
Year Established 2010 
Impact CamGaN was formed in 2010 to commercialise a novel technology (GaN LEDs on large-area (150 mm diameter) silicon) for the cost-effective manufacture of key components of high-brightness LEDs. This novel technology holds strong potential to dramatically reduce the cost of solid-state lighting devices that are rapidly replacing incandescent and fluorescent light bulbs. Plessey acquired CamGaN in 2012. In 2014 they manufactured over 2 million LEDS based on this technology. Recently they have raised £60m to expand production capacity and this will employ 400 more people in Plymouth. The widespread use of LED lighting in the UK will save 10% of all our electricity used and 10% of carbon emissions from power stations. We are continuing to develop this work on current EPSRC grants. See also my entry under my spin-out company Intellec.
Company Name INTELLEC LTD 
Description To further exploit our low-cost GaN LEDs on large area silicon. 
Year Established 2011 
Impact Intellec and CamGaN were taken over by Plessey in 2012. Plessey are now manufacturing millions of LEDs each year based on our technology. They are manufacturing in the UK, in Plymouth. Over 100 people are employed by Plessey in the UK on manufacturing our LEDs. Plessey raised £30 million from Deutsche Bank and £30 million from other investors in September 2015 to expand their manufacturing capabilities. Humphreys is a member of the Plessey Advisory Board. We continue to work with them on a variety of EPSRC grants. See also the entry under my spin-out company CamGaN.
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
Description Talk to visiting school group (Communications using light) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact An interactive talk on "Communication using Light" was delivered to a group of sixth formers visiting the department, incorporating elements on LiFi using LEDs and quantum communication using single photon sources.
Year(s) Of Engagement Activity 2016