Commercial exploitation of strained semiconductor alloys in communications, energy efficiency and consumer electronics
Submitting InstitutionUniversity of Surrey
Unit of AssessmentPhysics
Summary Impact TypeTechnological
Research Subject Area(s)
Physical Sciences: Other Physical Sciences
Engineering: Materials Engineering
Summary of the impact
Surrey's Photonics Group has played a pivotal role in understanding and
developing compound semiconductors for use in photonic devices. The
strained-layer quantum well technology proposed and developed in their
research is now incorporated in the vast majority of CD, DVD and blu-ray
systems, in telecommunications and the internet, in computer mice, and in
LEDs for solid-state lighting. Strained-layer quantum well lasers are
manufactured by industry in their millions annually with a market value
estimated in 2009 to be €15bn. Compared to the alternatives; these lasers
offer greater efficiency, which has opened up new applications.
The Group's research has expanded to develop semiconductors for use in
energy generation and combatting climate change, and in novel
photovoltaics, low energy internet communications, and greenhouse gas
detection. The research has led to engagement with the UK government's
energy minister and has stimulated public discussion around the world.
One of the key achievements of the underlying research can be traced back
to the mid-1990s when the idea of Prof. Alf Adams, FRS, for using strained
layers in quantum well lasers was verified theoretically and
experimentally . Prof. Adams and Prof. Eoin O'Reilly (who left the
University in 2000) showed that by deliberately incorporating a thin
semiconductor layer (i.e. a quantum well) with different lattice
constant to the host crystal substrate, the resulting strain would bring a
number of enhanced optical properties. These properties make lasers,
optical amplifiers and other optoelectronic components more efficient and
faster in operation. Strained-layer devices were demonstrated commercially
by Philips, working with Surrey researchers, and extended to applications
in high power laser diodes for manufacturing and printing. Adams extended
the idea of using strain from lattice mismatch to create non-absorbing
mirrors in high power lasers, as was described in a patent .
More recently, under the direction of Prof. Stephen Sweeney, the
Photonics Group has made large inroads into developing alternative III-V
material approaches for high efficiency lasers. They demonstrated that
1550 nm InGaAlAs quantum well buried heterostructure lasers offer superior
high temperature performance . Other research, in collaboration with Dr
Andreev (senior lecturer in the Photonics Group), described how p-doping
in InAs/GaAs quantum dots imparts improved temperature stability in
semiconductor lasers .
Research on quantum well lasers, published by the Group in 1999, showed
that even in the best strained-layer quantum well lasers, the efficiency
is governed by non-radiative Auger processes involving the spin-orbit band
. This finding led to work on new materials where the spin-orbit
splitting energy could be increased to remove the Auger processes.
Recently, another patent has been published by the Group  on an
entirely new class of III-V semiconductor (based on bismuth alloys), which
provides an optimised band structure offering power savings of 80% due to
loss suppression. The inclusion of bismuth in a III-V material increases
the spin-orbit splitting energy whilst reducing the band gap. When the
spin-orbit splitting energy exceeds the band gap energy, the major Auger
processes are inhibited, thus reducing the sensitivity of lasers to
changes in ambient temperature. Initial experimental evidence that this
concept can be achieved in practice was recently reported .
In parallel, the Photonics Group has been working closely with
EADS-Astrium to develop new semiconductor materials for photovoltaics to
capture solar energy in space. Highly efficient (>43%) photovoltaic
cells have been designed and tested at Surrey and are part of a pilot
programme to develop space-based solar power. This collaborative research
has formed the basis of a European Space Agency pilot study involving
Surrey to develop a fully working prototype.
References to the research
1. E. P. O'Reilly and A. R. Adams, "Band-structure engineering in
strained semiconductor lasers", IEEE Jour. Quant. Electr. 30,
pp 366-379 (1994) DOI: http://dx.doi.org/10.1109/3.283784.
This is one of the first papers theoretically and experimentally
verifying Surrey's strained-layer concept which now appears in almost
every semiconductor laser and LED produced in the world today.
This patent describes a method for using strain to create non-absorbing
mirrors. This method is now implemented in high power pump lasers for
4. I. P. Marko, et al. "Carrier Transport and recombination in p-doped
and intrinsic 1.3 µm InAs/GaAs quantum dot lasers", Applied Physics
Letters (2005) 87, 211114 (3 pages) DOI: http://dx.doi.org/10.1063/1.2135204 (51 citations)
5. A. F. Phillips, S. J. Sweeney, A. R. Adams and P. J. A. Thijs, "The
temperature dependence of 1.3- and 1.5µm compressively strained InGaAs(P)
MQW semiconductor lasers", IEEE Jour. Sel. Top. Quant. Electr., 5,
pp 401-412 (1999). DOI: http://dx.doi.org/10.1109/2944.788398
6. S. J. Sweeney, "Light emitting semiconductor device," GB patent
WO/2010/149978 and US patent 20,120,168,816. Available from: http://goo.gl/mHgBg
This patent application describes how bismuth may be used to develop high
efficiency photonic devices.
Prof. Adams and his collaborators held 14 EPSRC grants within the impact
period starting in 1993. An EPSRC LINK grant "Strained Layer Semiconductor
Materials" GR/G36142/01 (1991-94; valued at £207k) funded the research
leading to ref. 1. Research on quantum wells and quantum dots has
attracted significant investment through two Technology Strategy Board
programmes (totalling £3.7M) from 2003 to 2011 and led to outputs in .
Other funding: €3M EU BIANCHO project (July 2011 — July 2014; see www.biancho.org)
and £2M NSF/EPSRC/CRC/DPG Bismide Materials World Network project (Jan.
2011-April 2013; see www.bismides.net).
Bismides research is also central to a £1M EPSRC Leadership Fellowship
held by Prof. Sweeney (2010-2015).
Details of the impact
Surrey research on the concepts of strained-layer devices has made a
major economic impact. This impact was first achieved via close
interaction with the electronics firm, Philips N.V. They were prepared to
take the risk with what was considered at the time to be an unusual
approach, and in 2000 they licensed the Surrey patent (ref. 2) on using
strain to create non-absorbing mirrors. The technology proved to be
superior to other approaches existing at the time for telecommunications
applications. Philips (and later JDS) subsequently used the non-absorbing
mirror concept in the development of high power pump lasers, which are
used for optical amplification in telecommunications systems and to pump
high-power fibre lasers, such as those used in manufacturing.
The disruptive nature of the strained-layer technology forced all of the
other semiconductor laser manufacturers to adopt it. Dr. Andrew Carter,
the Chief Technology Officer at Oclaro, one of the world's largest
telecommunications companies, has stated that the Surrey research has
"revolutionised aspects of the design" of optoelectronic devices [Source
The majority of semiconductor-based photonics components now use
strained-layer quantum wells as embedded technology, which represents a
major economic impact of the research. According to Photonics21, the
European task force for photonics, the global market for these components
was around €15bn in 2009 and is expected to grow to >€30bn by 2015
[S2]. Furthermore, the component market levers much larger industries, e.g.
telecoms services worth more than €2 trillion at current estimates [S2].
As evidence of the reach of the economic impact of the research, it is
notable that almost all of the current known semiconductor laser
technology incorporates the strained-layer concept developed at Surrey.
Peter Selway, formerly the Director of Operations at Nortel, has
explained: "The use of appropriately strained layers gives benefits in
almost all aspects of the performance of semiconductor lasers, so much so
that laser engineers routinely use strain to fine-tune the performance of
virtually all lasers for all applications." [S3]
The strained-layer quantum well concept is now being employed in InGaN
based solid-state lighting, which is starting to become the core for all
future lighting technology. In this application, the ability to
incorporate strain provides a method of optimising the emission wavelength
of the InGaN LEDs used in solid-state lighting luminaires. The current
market for lighting is worth €50bn and is expected to grow to €100bn by
2020. Strained-layer quantum well LEDs are expected to form a core aspect
of this technology [S2]. The recently commercialised Philips LED lamp,
which was the recipient of the U.S.A. Department of Energy's first-ever "L
Prize" [S4], utilises strained quantum wells.
The new material reported in ref. 3 (Section 3) is now being implemented
in distributed feedback (DFB) and tunable lasers for telecommunications by
UK-based CIP and global telecoms giant, Oclaro, and is directly derived
from Surrey's research in the TSB-sponsored ETOE and ETOE2 projects.
Prof. Sugawara (Fujitsu, Japan) made use of the results of Surrey
research (ref. 4 in Section 3) when he set-up QD Laser Inc. to
commercialise the technology of quantum dot lasers. Their 1.3 µm quantum
dot lasers, which are currently commercialised, rely on p-doping to
provide temperature insensitivity. The mechanism by which this
insensitivity occurs and can be utilised was described in the Surrey
The Photonics Group's research in developing new semiconductor materials
and devices for renewable energy has made an impact on society by
capturing the public's attention and stimulating discussion. The research
has received wide exposure in international publications for general
audiences, such as The Economist [S5] (receiving >760 Facebook
likes, >100 re-tweets on Twitter, and >30 direct comments from the
public) and National Geographic [S6] (receiving >350 Facebook
likes, >130 re-tweets on Twitter, >100 Google+ recommendations and
10 direct comments from the public). The research was also highlighted in
national newspaper articles in The Independent, The Observer [S7]
(>70 direct comments from the public), The Sunday Times [S8],
the Times of India [S9], and more than ten trade journals in the
solar cell community. A television feature was produced by RAI (Italy) for
their Superquark popular science programme [S10], and a radio programme
was broadcast by ORF Radio (Austria). The potential of Surrey's recent
research on bismide materials to reduce the energy demands of the internet
was featured in the Financial Times [S11].
The Sunday Times article led to a direct request by the UK's
Energy Minister (Charles Hendry, MP) to visit the University to learn more
about the emerging field of research on using solar energy from space. Mr
Hendry commented: "The work that Prof. Sweeney of the ATI and his
colleagues are doing makes us realise that the way we'll be generating
electricity in 20 years' time is radically different to the way in which
it's being done today" [S12]. This ministerial visit and statement attest
the extent to which the Surrey activities are having an influence on
policy-makers. In addition, impact on industrial policy is made via
Sweeney's membership on Astrium's Photonics Strategy Group and
contributions to the UK Roadmap in Optoelectronics.
Sources to corroborate the impact
[S1] Video of Dr. Carter available at: http://bit.ly/1cGUFSI
[S2] "Photonics — Our vision for a key enabling technology of Europe",
European Technology Platform Photonics21, 2nd Edition, May
[S3] Former Director of Operations at Nortel. Contact details provided.
[S4] U.S.A. Department of Energy L Prize: http://www.lightingprize.org/
[S5] "Solar Power from Space: Beam it down Scotty", The Economist,
25th June 2011 (http://econ.st/1izbpQu).
[S6] "Beam it down, a drive to launch space-based solar power", National
Geographic Daily News, 5th December 2011 (http://bit.ly/1fWbL1s).
[S7] "How Britain can rejoin the space race", The Observer, 3rd
July 2011 (http://bit.ly/1h5VSZo).
[S8] "2021: a space power odyssey", The Sunday Times, 28th
August 2011 (http://thetim.es/1bGA6UB).
[S9] "Solar Harvest", Times of India, 7th November
[S10] Superquark "Centrali Solari Orbitanti", RAI TV, July 2010.
Available here: http://bit.ly/19HVNCr
[S11] "Laser redesign takes the heat off the internet", Financial
Times Magazine, 13th July 2012 (http://on.ft.com/1ivAhIS)
[S12] "The Next Generation", Total Politics Magazine, Jan 2012