EPSRC Manufacturing Fellowship in Gallium Nitride

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

Abstract

Gallium Nitride (GaN) based optoelectronic devices have the potential to revolutionise our society. They are more efficient and more robust than the alternative device technologies used today and therefore last longer and deliver significant energy savings. For example, GaN LEDs can be used to replace compact fluorescent and incandescent light bulbs in our homes and places of work. Such LED light bulbs have the potential to reduce by up to 50% the energy we use for lighting. Since about 20% of all the electricity we generate is used for lighting applications this would save the equivalent of about 8 power stations worth of electricity in the UK each year. Another, potentially even larger area where Gallium Nitride could have a significant impact is power electronics. Power electronic devices are found in electric cars, power supplies for laptop, and the control systems for mains electricity. Since GaN power electronics can handle more power, operate at higher voltages and are again significantly more efficient than other semiconductor technologies, it is estimated that by switching to GaN power electronics it may be possible to save up to £1 trillion each year in global energy costs.

From these examples it is clear that GaN devices can significantly help to reduce our demand for energy and therefore our Carbon footprint. However, for this potential to be realised, research still needs to be done to deliver the promised performance of these devices and to reduce their manufacturing cost so that they are widely accepted.

Production of semiconductor devices involves the manufacture of thousands or even millions of devices simultaneously on a circular wafer. One of the developments which has allowed the low cost and pervasive nature of Silicon electronics today are the economies of scale that can be achieved when large diameter wafer are used. A key step therefore in the manufacturing of low cost GaN devices is the development of high quality GaN layers grown onto large diameter Silicon wafers. This will allow the high volume production techniques that have been developed for the Silicon electronics industry to be applied for GaN devices reducing their cost by up to 80%.

Research carried out in this fellowship will provide new knowledge about how to grow and control GaN device layers. This will allow the promise of these devices to be realised enabling higher efficiencies, new applications and growth on large diameter Silicon substrates (upto 200mm). By carrying out this research in close collaboration with UK industry, the developments will be focused towards real products and address some of the real world challenges associated with delivering high performance and reliable devices. This will also ensure that the research supports the developing GaN device manufacturing base in the UK and can contribute to the commercial exploitation of GaN technology.

Planned Impact

Gallium Nitride (GaN) devices have the potential to address some of the major challenges currently facing society. The high efficiency with which GaN can convert electrical energy in to light and control electrical energy means that such devices can reduce electricity consumption by 10's of percent, contributing to reduced carbon emissions and saving billions of pounds. Thus the research to be carried out in this fellowship will contribute to many of the Government led initiatives in the UK and across the world aimed at reduced energy usage, improved energy security and reduced green house gas emission. By contributing to the delivery of efficient GaN devices, the outputs of this research will tackle these goals and have an impact on how policy makers plan to address issues such as the integration of renewable energy sources and delivery of environmentally friendly transport policies.
There are a significant number of companies in the UK currently developing products based on GaN. For example Plessey, NXP, International Rectifier and IQE(Europe) are all actively developing GaN technologies. Through my links to these industries the improvements in GaN materials technology delivered by this fellowship will be rapidly available for incorporation in to future and existing projects allowing results to be exploited on very short timescales, i.e. less than 1 year in some cases. Additionally, there are a number of supply industries which support these manufacturing capabilities such a Laytec UK who produce in-situ growth monitoring systems, Aixtron UK who manufacture MOCVD growth systems and Oxford Instruments who build GaN processing tools. I already have established links with many of these commercial organisations as a result of my current research activates. This fellowship will provide opportunities to strengthen and widen these interactions, contributing to the whole GaN technology supply chain in the UK. Existing interactions with these industries include both collaborative development projects and testing of measurement systems in a manufacturing environment. Close links with these commercial activities are important for the delivery of devices compatible with real world applications since many of the manufacturing and reliability issues can only be addressed by performing trials in a volume production environment with the highly reproducible processes that this delivers. Here my intimate knowledge of the volume production facilities at Plessey and future access to these offer a unique opportunity to bridge the gap between research and manufacturing.
Apart from companies involved directly with GaN materials and devices there are also a large number of organisations developing system level products based on GaN technologies. These include >100 companies developing lighting products (Luminaires) based on GaN LEDs. The Cambridge centre for GaN already has links and provides advice to some of these companies, for example Forge Europa, and along with my own contacts, this fellowship position within the University will provide me with more freedom to interact with these organisations without the limitations of specific commercial interests.

Through the delivery of more efficient lighting and power systems and contributing to the delivery of government policy, this fellowship will also have an impact on the general population both in the UK and globally. This will be seen through improved quality of life enabled by the tackling of climate change and reduction of fuel poverty. A direct benefit to the population of the UK will be seen through reduced energy bills as more efficient lighting and power control systems are made available in our homes and businesses. It is possible that such benefits could begin to be seen within the 5 year period of this fellowship as the commercial take up of GaN devices accelerates.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
EP/N01202X/1 01/03/2016 30/04/2017 £1,270,945
EP/N01202X/2 Transfer EP/N01202X/1 01/05/2017 28/02/2022 £1,061,742
 
Description The research funded on this grant has allowed development of the growth and Characterisation of GaN-based device structures. Key finds are in two areas; firstly in the area of GaN high power electronic devices which offer higher frequency, higher power and higher efficiency operation compared to conventional device technologies. The second area is in the growth of cubic-GaN. This has the potential to overcome some of the challenges with conventional GaN LEDs and will allow higher efficiency green LEDs to be developed to give better displays and LED light bulbs
Exploitation Route The cubic phase of GaN is not as well understood as the standard hexagonal phase. The process that has been developed to grow high quality cubic GaN films has already allowed new collaborations to be established with the universities of Manchester and Strathclyde to study this material. Along side this a spin-out company called Kubos Semiconductors has been formed to commercially exploit the technology to develop efficient green LEDs
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Energy

 
Description Research carried out in to the growth of the cubic form of Gallium Nitride (GaN) has lead to the formation of a spin out company, Kubos Semiconductors Ltd. Kubos will take forward the exploitation of the cubic GaN technology to allow commercial benefit to be realized from the production of efficient green LEDs
First Year Of Impact 2017
Sector Electronics
 
Description The Energy Entrepreneurs Fund
Amount £483,000 (GBP)
Funding ID EEF6084 
Organisation Department for Business, Energy & Industrial Strategy 
Sector Public
Country United Kingdom
Start 10/2018 
End 09/2020
 
Title Research data supporting "Effect of growth temperature and V/III-ratio on the surface morphology of MOVPE-grown cubic zincblende GaN" 
Description Figure 1: XRD intensity profile through the 1-103wz and 113zb reflections for the samples grown on a 4° miscut substrate at 875°C and a V/III-ratio of 76 (a), and 1200 (b). Figure 4: Feature sizes in (a) [110] and (b) [1-10] directions extracted from 2D-FFT of AFM height data of zb-GaN epilayers grown at different growth temperatures and a constant V/III-ratio of 76. (c) Variation of the aspect ratio of surface features with growth temperature. (d) Variation of root mean square surface roughness with growth temperature. Figure 5: Zb-GaN content determined by XRD as a function of the GaN epilayer growth temperature. Figure 8: Feature sizes in (a) [110] and (b) [1-10] directions extracted from 2D-FFT of AFM height data of the zb-GaN epilayers grown at different V/III-ratios and a constant growth temperature of 875 °C. (c) Variation of aspect ratio of surface features with V/III ratio. For (a) to (c), there are no data points for the sample grown at a V/III-ratio of 15, as it was not possible to extract feature sizes using the same 2D-FFT method as for other sample in the series. (d) Variation of root mean square surface roughness with V/III-ratio. The labels i, ii and iii indicate the proposed growth regimes. Figure 11: Relative intensities of the zb-GaN XRD peaks for samples in the V/III-ratio series at a constant growth temperature of 875 °C. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Research data supporting "Effect of growth temperature and V/III-ratio on the surface morphology of MOVPE-grown cubic zincblende GaN" 
Description Figure 1: XRD intensity profile through the 1-103wz and 113zb reflections for the samples grown on a 4° miscut substrate at 875°C and a V/III-ratio of 76 (a), and 1200 (b). Figure 4: Feature sizes in (a) [110] and (b) [1-10] directions extracted from 2D-FFT of AFM height data of zb-GaN epilayers grown at different growth temperatures and a constant V/III-ratio of 76. (c) Variation of the aspect ratio of surface features with growth temperature. (d) Variation of root mean square surface roughness with growth temperature. Figure 5: Zb-GaN content determined by XRD as a function of the GaN epilayer growth temperature. Figure 8: Feature sizes in (a) [110] and (b) [1-10] directions extracted from 2D-FFT of AFM height data of the zb-GaN epilayers grown at different V/III-ratios and a constant growth temperature of 875 °C. (c) Variation of aspect ratio of surface features with V/III ratio. For (a) to (c), there are no data points for the sample grown at a V/III-ratio of 15, as it was not possible to extract feature sizes using the same 2D-FFT method as for other sample in the series. (d) Variation of root mean square surface roughness with V/III-ratio. The labels i, ii and iii indicate the proposed growth regimes. Figure 11: Relative intensities of the zb-GaN XRD peaks for samples in the V/III-ratio series at a constant growth temperature of 875 °C. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Research data supporting "X-ray diffraction analysis of cubic zincblende III-nitrides" 
Description Figure 6: XRD peak width of an optimized zincblende GaN sample displayed in a traditional Williamson-Hall plot with fits for Lorentzian (n = 1) and Gaussian shape peaks (n = 2). Figure 7: Extrapolated peak width ß_hkl ×|Q_hkl| in reciprocal space as a function of polar angle Chi and scattering vector magnitude |Q_hkl| estimated from a series of skew-symmetric ?-scans. Figure 8: Decrease of the XRD ?-linewidth (FWHM) of the 002 reflection with increasing film thickness for oriented zincblende GaN grown on 3C-SiC at Cambridge University. Figure 9: An example for a XRD wafer bow analysis of a 4'' 3C-SiC/Si template showing the shift of the maximum of ?-scans at different positions on the wafer. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Research data supporting "X-ray diffraction analysis of cubic zincblende III-nitrides" 
Description Figure 6: XRD peak width of an optimized zincblende GaN sample displayed in a traditional Williamson-Hall plot with fits for Lorentzian (n = 1) and Gaussian shape peaks (n = 2). Figure 7: Extrapolated peak width ß_hkl ×|Q_hkl| in reciprocal space as a function of polar angle Chi and scattering vector magnitude |Q_hkl| estimated from a series of skew-symmetric ?-scans. Figure 8: Decrease of the XRD ?-linewidth (FWHM) of the 002 reflection with increasing film thickness for oriented zincblende GaN grown on 3C-SiC at Cambridge University. Figure 9: An example for a XRD wafer bow analysis of a 4'' 3C-SiC/Si template showing the shift of the maximum of ?-scans at different positions on the wafer. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title ZINCBLENDE STRUCTURE GROUP III-NITRIDE 
Description A method is disclosed of manufacturing a semiconductor structure comprising an (001) oriented zincblende structure group III-nitride layer, such as GaN. The layer is formed on a 3C-SiC layer on a silicon substrate. A nucleation layer is formed, recrystallized and then the zincblende structure group III-nitride layer is formed by MOVPE at temperature T3 in the range 750-1000 ºC, to a thickness of at least 0.5µm. There is also disclosed a corresponding semiconductor structure comprising a zincblende structure group III-nitride layer which, when characterized by XRD, shows that the substantial majority, or all, of the layer is formed of zincblende structure group III-nitride in preference to wurtzite structure group III-nitride. 
IP Reference WO2018178315 
Protection Patent application published
Year Protection Granted 2018
Licensed Yes
Impact This patent application has lead to the formation of a spin-out company called Kubos Semiconductors limited. To date this company has several employees and has raised >£300k in private capital
 
Company Name Kubos Semiconductors Ltd 
Description Kubos will promote the commercial exploitation of cubic GaN technology for the production of efficient green LEDs 
Year Established 2017 
Impact Kubos Semiconductors Ltd has to date raised £500k in private funds and has been awarded an Energy Entrepreneurs Fund grant of £490k to fund development of cubic GaN technology and develop its business
Website https://www.kubos-semi.com/
 
Description Presentation at Manufacturing 2075 event at university of Cranfield 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Approx 40 school children attended the presentations and then participated in workshops to discuss manufacturing requirements for the future. This increased their awareness of STEM activities in Manufacturing and prompted them to consider how the manufacturing of future products could be improved
Year(s) Of Engagement Activity 2017
URL https://www.cranfield.ac.uk/events/manufacturing-2075-landing/manufacturing-2075--2017-virtual-sympo...
 
Description Public presentation for the school of physical sciences at university of Cardiff 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact This presentation was part of a series of talks which is intended to expose the research activities at the university of Cardiff to a broad audience
Year(s) Of Engagement Activity 2017