Defence R & D and the UK electronics industry

Defence funding played a major part in the development of the UK electronics industry, providing both a market for products and a major source of R & D funding. For many years defence support for electronics R & D was provided through a Ministry of Defence (MoD) organization known as CVD. Originally set up before the Second World War as the Inter-Services Committee for the Coordination of Valve Developments, CVD sought to rationalize the burgeoning number of specialist committees involved in the application of valve technology to warfare.Footnote ¹⁷

Over the years, CVD's role grew from coordination to active sponsorship of industrial electronics R & D geared towards military objectives. In keeping with the shifting emphasis of technology away from valves and towards semiconductors, the acronym of CVD was retained whilst the organization was formally renamed as the Directorate – Components, Valves and Devices in 1972.Footnote ¹⁸

CVD's influence on UK electronics R & D was huge. During the 1950s and 1960s, MoD funding of electronics R & D in the UK far exceeded any other external source, and was often greater than the industry's own R & D expenditure.Footnote ¹⁹ Although CVD support came to be matched by that of the Department of Trade and Industry (and its predecessors), it remained a major source of R & D funding up until the demise of CVD in 1992.

Defence-related electronics R & D was carried out at, or in collaboration with, the defence research establishments. The two main establishments involved were the Royal Radar Establishment (RRE) at Malvern and the Services Electronics Research Establishment (SERL) at Baldock, which were amalgamated to form the Royal Radar and Signals Establishment (RSRE) in 1976.Footnote ²⁰

Although the explicit policies and organizational arrangements regarding civil spin-off have varied over the years, the underlying attitudes of staff working on electronics technology were always supportive of rapid civil uptake. This was especially the case at the Radar Research Establishment at Malvern where research was more basic in orientation, especially during and after the period when it was part of the Ministry of Technology (MinTech) in the late 1960s. The Services Electronic Research Laboratory at Baldock and Harlow, which remained outside MinTech, was more directly geared towards the development of service equipment. Nevertheless, the general view at both establishments was that early civil uptake of new electronics should be encouraged because it was likely to result in the development of more cost-effective manufacturing processes.Footnote ²¹

Of course, both CVD and the research establishments were primarily motivated by the interests of the armed services, and not explicitly by any broader effects on the UK economy. However, there was recognition that a strong UK microelectronics industry was important for UK defence requirements. For example, a joint meeting of the MoD's Weapons Development and Defence Research Committees on 25 May 1966 to consider the use of microelectronics in defence equipment ‘agreed in principle that it was in the interest of Defence to assist in the urgent building up of the British microelectronics industry.’Footnote ²² The question of broader support for British electronics did of course raise questions about who would pay for this. CVD discussion of the matter concluded that ‘the CVD budget was approved fundamentally for expenditure in the defence field. CVD would, however, be perfectly willing to operate on the behalf of the Ministry of Technology if further monies could be supplied for this purpose’. Even then, of course, there was ‘also a problem with the definition of “what was a UK firm”, and this remained something which the Ministry of Technology had to define’.Footnote ²³

CVD contracts, possibly followed by defence procurement, provided one potential channel for industrial exploitation. This was complemented by the work of the National Research Development Corporation (NRDC) that had the formal responsibility for the exploitation of inventions stemming from UK public-sector R & D from 1950 to 1985.Footnote ²⁴

In practice this meant that NRDC would take on inventions stemming from the work of the research establishments so long as they were not unsuitable for reasons of national security, nor the result of collaboration in which the industrial contractor would be assigned the intellectual property rights. The relationship between NRDC and the research establishments peaked in the 1960s with the advent of the Ministry of Technology.Footnote ²⁵ Both the Royal Radar Establishment at Malvern and NRDC came under the jurisdiction of MinTech, which sought to increase civil exploitation of the defence technology base.

Amongst the initiatives promoted by MinTech, the most directly concerned with semiconductor materials was the setting up in 1967 of an Electronic Materials Unit (EMU) within the Royal Radar Establishment. This was intended to supply newly available semiconductor materials to be used by industry, universities or other government research establishments, thus avoiding the necessity for each to produce their own.Footnote ²⁶

The EMU at Malvern was, like MinTech, short-lived. A longer-lived embodiment of the collaborative spirit underlying defence-funded semiconductor R & D was the Gallium Arsenide Consortium.Footnote ²⁷ Set up in 1966 under the aegis of CVD, the consortium brought together staff from RRE and SERL with the main CVD contractors – Plessey, STL (Standard Telecommunications Laboratories), BDH (British Drug House) Chemicals, Mullard, and GEC (General Electric Company) – who were active in semiconductor materials work.Footnote ²⁸ Of these, Mullard, based at Mitcham, was owned by the Dutch Phillips company, and STL, the R & D wing of STC (Standard Telephones and Cables) was owned by the US ITT Corporation.

Because of its potential for radar use, the microwave capability of gallium arsenide gave development of the material high priority at Malvern (although it would be many decades before GaAs could compete with older technologies such travelling wave tubes, magnetrons and klystrons for radar applications that required high power outputs). The other main attribute of III–V materials, their opto-electronic characteristics, was initially investigated mainly at Baldock. The much-publicized advantage of gallium arsenide over silicon – that its operation at higher frequencies meant it was faster – turned out not to find much practical application, although emphasis of this apparent advantage over silicon may have been politically useful.Footnote ²⁹

Device development

The first useful devices made from III–V materials were light-emitting diodes (LEDs). These can be made by simply connecting leads to a suitable piece of III–V material with the emission of visible radiation occurring when voltage is applied across a p-n junction. A number of materials were found to work as LEDs, including GaAs, gallium phosphide (GaP), gallium arsenide phosphide, and indium phosphide.

SERL was particularly active in LED development and in 1963 claimed the world's first practical application of GaP with an LED array developed to mark positional data on the TSR2 aircraft's reconnaissance film.Footnote ³⁰ In 1964 Ferranti took over production of the arrays from SERL.Footnote ³¹ Other arrays were developed at SERL during 1964 for the Atomic Weapons Research Establishment as part of accurate time-recording equipment for nuclear testing and for the joint US/UK re-entry physics experiments using Black Knight rockets.Footnote ³²

With the technology thus proven, SERL withdrew from LED development, noting, ‘Requirements for the present gallium phosphide lamps can now be adequately met by industry and this part of the device programme is terminated.’Footnote ³³ CVD continued to support LED development (both GaP and GaAs) during the rest of the 1960s with requirements for military systems being met by UK industry.Footnote ³⁴ In particular, Plessey and Ferranti began work on GaP ‘with a view to exploiting the use of semiconductor lamps’.Footnote ³⁵

However, SERL's work with Plessey and Ferranti to develop LEDs left little industrial legacy ‘largely because neither company was interested in investing in it’.Footnote ³⁶ CVD's Technical Committee complained in 1974 that it ‘had funded GaP research at Ferranti and the work had gone well but the firm was not willing at this time to undertake production’.Footnote ³⁷ In 1975 CVD reported,

The difficulty of establishing a viable indigenous LED manufacturing industry, despite CVD's support and the work of SERL, led to much soul-searching. CVD's Display Devices Research Panel, chaired by Cyril Hilsum, noted,

Thereafter, Plessey was the sole UK producer of LEDs, although Hilsum noted bitterly that ‘to keep them in business, CVD must subsidise them’.Footnote ⁴⁰ Plessey apparently remained unconvinced that the commercial returns justified a large investment on their part:

In fact, Plessey did remain in LED manufacturing, but mainly supplying markets such as defence and avionics because it was ‘not really in that large-volume, low-price business’.Footnote ⁴² Its LED business was taken over by a management buyout just prior to Plessey's takeover by GEC and Siemens in 1989, and has since operated successfully as PRP Optoelectronics, albeit as a niche producer.Footnote ⁴³

LEDs were a simple application of the opto-electronic properties of III–V materials, but the ability of these materials to absorb or emit photons also meant that they could be used to build lasers and photocathodes for night vision. Work on these started in the 1960s, but it was developments in epitaxial growth techniques that really brought them to maturity and so they are discussed below.

However, although the opto-electronics properties were the first to be exploited, ‘the original choice of GaAs was for use as a transistor material, where the higher band gap would allow higher temperature operation and the high mobility higher frequencies of operation than obtainable with silicon’.Footnote ⁴⁴ These theoretical advantages proved hard to realize, and when CVD's Policy Committee's Research Advisory Panel reviewed the CVD Research Programme on 31 March 1965 it concluded ‘that, under normal conditions, GaAs transistors had few advantages over other transistors, but that they might be valuable under conditions of high operating temperature’.Footnote ⁴⁵

This pessimistic conclusion followed some frustrating work done by a SERL-led consortium involving STC, Marconi Research, Plessey Caswell and RSRE ‘under the iron-fisted chairmanship of Cyril Hilsum’.Footnote ⁴⁶ With little progress to show, this was terminated after two years at the end of 1964.Footnote ⁴⁷ After being told that the project was to be terminated, the Caswell contingent, while driving home, ‘vowed to continue the transistor work in GaAs in some form or other and even before the return journey was complete it was agreed to propose to the MoD that work begin on a gallium arsenide field effect transistor’ (FET).Footnote ⁴⁸

Plessey had the advantage of good-quality in-house material. In the early 1960s Plessey developed a process for producing gallium arsenide in which gallium and arsenic trichloride vapours were combined to grow epitaxial layers on a substrate.Footnote ⁴⁹ This was acknowledged by CVD's Solid State Physics Research Panel, which reported that ‘a process has been developed [at Plessey] to make high purity GaAs of quality superior to that made elsewhere in the world’.Footnote ⁵⁰ However, the first device to make use of this material was not a transistor, but a microwave-generating oscillator known as the Gunn diode.Footnote ⁵¹

Although named after J. B. Gunn, an English scientist who had moved to work at IBM in the USA in 1959, the Gunn diode was based on an effect earlier predicted by work at the Mullard Research Laboratories in Surrey and at SERL.Footnote ⁵² The UK's early emphasis on III–V materials R & D meant that, uniquely in the history of semiconductor developments to that date, the first commercial production of Gunn diodes occurred in the UK, not the USA. In 1965 Associated Semiconductors Manufacturers (ASM), a subsidiary of Mullard, in conjunction with GEC, began production of gallium arsenide Gunn diodes, and other UK manufacturers followed shortly thereafter.Footnote ⁵³

The Gunn effect meant that gallium arsenide could provide a cheap, compact, low-power microwave source with potential use in radar and communications technology. Applications based on gallium arsenide Gunn diodes were one of the widely advertised examples of civil spin-off used to promote the work of the Industrial Applications Unit at the RRE, Malvern.Footnote ⁵⁴ Civil applications in development included burglar alarms and portable ‘speed guns’.

Such potential for civil exploitation of the UK's gallium arsenide expertise was a matter of interest to CVD in the mid-1960s:

In the meantime, Plessey's work on GaAs FETs during the 1960s eventually paid off with the announcement in February 1970 of the GAT 1, ‘the first commercially available GaAs FET.’Footnote ⁵⁶ Although this particular device ‘did not perform as predicted by the theory available at the time’, the development of the FET offered the prospect of high-frequency, low-noise amplification.Footnote ⁵⁷ Caswell continued during the 1970s with work on MESFETs (metal semiconductor field effect transistors) and in July 1977 the chairman of CVD's Power Devices Research Committee noted that Plessey's GaAs work ‘continues to extend the performance of microwave FET amplifiers to higher frequencies, higher power and low noise, and the team at Plessey receives world-wide recognition’.Footnote ⁵⁸ Of particular significance was the demonstration of the first GaAs FET-based monolithic microwave integrated circuit (MMIC) in 1976.Footnote ⁵⁹

This development of transistors operating at microwave frequencies (and thus usable for amplification in radar systems) really became a practical proposition when good-quality semi-insulating GaAs substrate became available. Plessey's epitaxial growth process provided material for their research, but during the 1960s bulk GaAs substrate was typically made by the Bridgman process in which a pressurized, horizontal crucible of polycrystalline GaAs is heated from one end to the other. Seeded with a crystal, this results in virtually all the crucible contents crystallizing so that impurities are in effect moved through the crucible as it is heated so that the final section of the crystal can be discarded with the impurities.

However, the Bridgman process produced semi-conducting GaAs and its low resistivity makes it unsuitable for high-frequency applications because low resistivity GaAs is susceptible to interference within a ‘chip’. To make this material semi-insulating requires the Bridgman-produced ingots to be doped heavily with chromium, and ‘radial non-uniformity made this material less than satisfactory’.Footnote ⁶⁰ An important development in materials production was thus the development of crystal ‘pullers’ (see next section) that could produce good-quality undoped semi-insulating GaAs which then enabled the production of integrated circuits (ICs) using ion implantation: ‘High performance FETs fabricated using this technology were first demonstrated in 1977.’Footnote ⁶¹

With the development of the MMIC and with suitable bulk GaAs becoming available, Caswell was now able to produce devices for military phased-array radars in which each radar element comprises a single transmit/receive device. Other applications also beckoned and during the 1980s Plessey ‘took management control of the facility at Caswell’ and ‘set itself up … to have a commercial presence in gallium arsenide … not just for in-house specials; it was going to be a commodity supplier’.Footnote ⁶²

However, the takeover of Caswell by GEC in 1989, and the establishment of GEC-Marconi Materials Technology Ltd in 1991, saw investment in GaAs production facilities, but also an orientation more towards defence-procurement markets.Footnote ⁶³ Although there was a significant civil market for optical modulators for communications systems, Caswell found itself in the familiar ‘dual-use’ conundrum of attempting to be effective as both a defence-procurement supplier and a commercial operator.Footnote ⁶⁴ As noted by one commentator, ‘the constant battle between internal defence needs and the external commercial aims is a challenge that few defence operations have successfully pulled off’.Footnote ⁶⁵ According to one SERL/RSRE scientist, GEC ‘maintained a capability to make these devices in the UK, and they are very good, they are world competitive, but they are not commercial’.Footnote ⁶⁶

When Marconi demergered, Caswell was taken over by the US-based Bookham Technology in 2002, and in 2004 Caswell's GaAs production line was closed down. This ended over forty years of work on GaAs, said to be the longest continuous such activity anywhere.Footnote ⁶⁷ This was not the end of GaAs device manufacturing in the UK, however. In 1999, with the help of a £5 million UK government grant, Filtronic took over Fujitsu's silicon foundry at Newton Aycliffe in Country Durham and converted it to GaAs production, particularly aimed at the growing market for mobile phone devices. Filtronic's foundry became the largest GaAs device producer in Europe. However, even then Filtronic was not in the top ten GaAs device producers worldwide, a list dominated by US companies.Footnote ⁶⁸ Moreover, the Newton Aycliffe plant returned to foreign ownership in 2008 when Filtronic sold its compound semiconductor operations to the US RF Micro Devices.Footnote ⁶⁹

Material production and crystal pullers

One of the biggest successes of UK defence-sponsored work was the development of crystal growth systems that could be used to produce III–V materials such as gallium arsenide, indium phosphide and gallium phosphide. From the mid-1950s materials work at SERL was dominated by efforts to produce gallium arsenide of sufficient quality to investigate its properties. Initially, GaAs ingots were produced by the ‘floating zone’ technique that involved solidification of a horizontal bath of molten GaAs. In 1960 the SERL Technical Journal noted that ‘the quality of the average ingot is now better than that available elsewhere. There is still no other British source of high-grade material, but several firms are beginning production on an experimental scale’.Footnote ⁷⁰

This production method was possible with GaAs, but not with gallium phosphide (GaP) and commercial exploitation of GaP LEDs was held back by the lack of an efficient production process. Instead, the less efficient gallium arsenide phosphide captured most of the initial market for LEDs.Footnote ⁷¹ GaAsP could be built up on a GaAs substrate by adding phosphorous to a GaAs vapour.

Both SERL and RRE had used Czochralski pullers to produce silicon and germanium and they now applied the technique to GaP.Footnote ⁷² The Czochralski technique was a proven approach for growing semiconductor crystals by slowly pulling a crystal out of melted liquid. However, gallium phosphide was particularly difficult to grow because it dissociates at its melting point, making the standard approach impractical. To overcome this, RRE developed a modification of the technique in which the surface of the semiconductor melt is covered with a viscous liquid (boric oxide) to suppress loss of volatile components.Footnote ⁷³ Known as the liquid-encapsulation Czochralski (LEC) technique, this approach was then adapted to high-pressure vessels and taken up by Metals Research Ltd under licence from the National Research Development Corporation.Footnote ⁷⁴ NRDC contributed a joint share of development funds in return for a levy on sales.Footnote ⁷⁵ Metals Research's first puller sale was to Bell Labs in the US, with the second one going to Plessey Caswell.Footnote ⁷⁶

Known as the ‘Malvern’, this crystal puller became the standard method for producing GaP crystals, with the pullers themselves selling particularly well in Japan.Footnote ⁷⁷ Improvements in the Malvern meant that between 1969 and 1975 the size of crystal that could be produced went from fifty grams one kilogram.Footnote ⁷⁸ However, this was still not enough to make GaP production competitive with that of GaAsP, and the Malvern also suffered from difficulties with its lack of user-friendliness and unevenness of crystal quality.

Metals Research therefore developed a new crystal puller, the Melbourn (named after the village near Cambridge where Metals Research was based), which addressed these problems. Larger than the Malvern, it was designed to produce high-quality crystals weighing up to seven kilograms. Moreover, whereas the Malvern was adapted from RRE's laboratory design, the Melbourn was designed from scratch as a production machine, with ease of operation a main concern. Another improvement stemmed from work at RRE to develop automatic diameter control (ADC). One of the difficulties involved in Czochralski growth is instability that tends to produce a crystal ingot of very uneven diameter. RRE's approach, now widely used in crystal growth of many materials, maintains an even crystal diameter through temperature feedback based on the rate of the increase in the crystal's weight. Working together, RRE and Metals Research produced a world-leading design: ‘The result of this pooling of the intellectual resources, experience and expertise of both establishments was a workable system, and a properly engineered version of this has now been incorporated into the new Melbourn puller.’Footnote ⁷⁹

During the 1970s, Metals Research exported its pullers all over the world, with particularly strong demand in the US and Japan. The pullers were sold on a ‘turn-key’ basis as a ‘technology package’ that included setting up the machine and doing enough growth runs to provide guaranteed performance.Footnote ⁸⁰ As Roger Waldock of Metals Research joked, this could take two weeks to do at Westinghouse in Pittsburgh in the winter, but three months at Hughes in Malibu in the summer.Footnote ⁸¹ This, of course, meant that at the same time as it was being successful in selling the crystal pullers, Metals Research was also exporting technology that would enable overseas firms to compete strongly in crystal production.

In fact, Japan very quickly came to dominate the production of GaP, largely based on the use of Metals Research machines:

Established as the way to make GaP crystals, Metal Research's pullers then became of interest for GaAs production. Although the LEC approach had been investigated for GaAs production, it was thought unsuitable because of the interaction with the boric oxide encapsulant. In any case, gallium arsenide did not need to be made by the LEC technique because it could be made by the Bridgman process.

Bridgman remains a major source of GaAs crystals because it is cheaper than LEC and generally produces a better crystal structure, which is important for opto-electronic applications. However, the Bridgman process was not ideal for producing GaAs material for microwave applications – Malvern's main interest – because the crucibles are made of silica and the subsequent contamination of the material with silicon complicates the production of semi-insulating properties.Footnote ⁸³ With concerns over the supply of semi-insulating GaAs, CVD's Applied Physics Panel ‘invited Metals Research to submit a proposal for pulled material’ in 1975.Footnote ⁸⁴

The next, very significant, step stemmed from work (both in the US and at Metals Research, which in 1975 took over, and adopted the name of, Cambridge Instruments) that showed that LEC GaAs crystals could be grown with semi-insulating properties without chromium doping if silica was not present.Footnote ⁸⁵ Initially, this meant using crucibles made of pyrolytic boron nitride, but then Cambridge Instruments discovered that the same effect could be achieved using silica crucibles so long as the moisture content of the boric oxide encapsulating layer was carefully controlled.Footnote ⁸⁶

This LEC-pulled GaAs also had the added benefit that the cylindrical ingots produced could be cut into cylindrical wafers that ‘were highly desirable if the processing technology established for silicon ICs was to be taken over and adapted to gallium arsenide’. As a result the Cambridge ‘pullers quickly came to dominate the world market for pressure pullers and the materials base for a gallium arsenide IC technology was founded’.Footnote ⁸⁷

Cambridge Instruments thus repeated the export success that it had first had with its GaP pullers. During the 1980s interest in semi-insulating gallium arsenide led to worldwide sales for Cambridge Instruments pullers (in 1987 it was estimated that 80 per cent of pullers installed for GaAs manufacture in the US had been built by CambridgeFootnote ⁸⁸). However, by the end of the 1980s the market for pullers had tailed off. Not only had most potential customers already acquired all the pullers they wanted, but limited demand led others to stop gallium arsenide production, leading to the availability of second-hand pullers. In some cases, the initial desire for a puller was to ensure an in-house supply of material for R & D purposes (in, say, device development), a requirement which became unnecessary once satisfactory material became reliably available on the open market.Footnote ⁸⁹

As well as producing the pullers, Cambridge Instruments also produced and sold some III–V materials, mainly for R & D purposes or for military applications. Ironically, the large number of Metals Research/Cambridge pullers supplied to Japan made it hard to compete. As one of the key figures in the development of pullers at Metals Research/Cambridge noted, ‘The Japanese wiped us out as well as everyone else in the GaP business, and we went into GaAs.’Footnote ⁹⁰ However, although Cambridge Instruments dominated the world market for high-pressure pullers, they were not so successful in producing the final GaAs product themselves, and it was noted that whilst ‘the CI pulling technology is in the van of world development, they have been overtaken by several foreign suppliers in wafer finish’.Footnote ⁹¹

In 1985, the materials production side of the business was sold to ICI Wafer Technology, which set up a new factory at Milton Keynes for the production of gallium arsenide and indium phosphide. Substantial investment by ICI led to improvements in the quality of wafer finishing, but at the end of the 1980s ICI corporate policy was reconsidered, and the move into semiconductors was reversed.

ICI was not the only company to have invested in gallium arsenide production, and production capacity exceeded demand in the late 1980s, leading to several withdrawals from the market. Mining Chemical Products (MCP), the other main UK producer of GaAs and other III–V materials – using a Bridgman method – was also finding market conditions difficult. As a result, in 1990 MCP took over the ICI Milton Keynes plant (and relocated there from its site at Woking) to form Wafer Technology. In 1994 MCP then also decided to move out of electronic materials and a management buyout took control of Wafer Technology (four managers took a majority holding of 80 per cent, with MCP retaining the remaining 20 per cent).

Wafer Technology (now a subsidiary of Cardiff-based IQE plc) continues to make materials using both LEC and vertical gradient freeze techniques. These include LEC-produced indium phosphide, which has become increasingly used in fibre-optic telecommunications applications because it is particularly suitable for making devices that emit or detect at frequencies (1.3 and 1.55 microns) which provide the best transmission through fibre optics.

Wafer Technology also continues to make LEC GaAs, but mainly for customers who use it for research purposes. The main market for LEC GaAs now involves larger wafer sizes for use in device production, but intense competition for these sizes led to prices that Wafer Technology could not economically match. American investment in this area was driven by the ‘Title III’ programme that was initiated in 1994 and provided US government support to build up a national gallium arsenide capacity.Footnote ⁹² According to US Deputy Undersecretary of Defense for International and Commercial Programs,

However, by 1998 the situation had changed so that ‘these companies dominate the U.S. and world markets with nearly 60 percent of the market and world-class product quality’.Footnote ⁹³ More recently, Japanese companies Sumitomo and Hitachi, alongside the German Freiberger Compound Materials, have taken over as the leading producers. Although Wafer Technology continues to fly the flag for the UK in production of III–V materials, it is now a niche producer.

Epitaxial growth

Semiconductor wafers are the basic building blocks of electronics, but most devices also make use of epitaxy, in which precise layers of semiconductor are laid down on the wafer substrate. This is used to control the semiconductor properties and to develop devices. Initially the most successful approach, liquid-phase epitaxy (LPE) was limited in its potential for high performance because of lack of precise control over both the sharpness of the transition between the epitaxial layers and the evenness of layers across the whole wafer. Two other epitaxial techniques offered better performance: metal organic chemical vapour deposition (MOCVD), also known as metal organic vapour phase epitaxy (MOVPE); and molecular beam epitaxy (MBE).

UK work on MOCVD was pioneered at SERL under Sidney Bass.Footnote ⁹⁴ Named after its inventor, the Bass reactor allowed thin layers of material to be built up on the semiconductor wafer surface. In particular, the organic-based process (originally conceived by Hal Manasevit in the US) allowed the deposition of materials that could not be carried by the previous chlorine-based process because of their reactive nature. This was crucial because it opened up the potential for mixing aluminium arsenide (which was too reactive for chlorine-based epitaxy) with gallium arsenide to fine-tune semiconductor properties.Footnote ⁹⁵

SERL's work led to ‘the world's first volume production of metal organic gallium arsenide’ in the manufacture of an image-intensifying photocathode for military use.Footnote ⁹⁶ This proved to be ‘an unexpectedly difficult development’, with the work started at SERL in the mid-1960s not coming to fruition until the 1980s.Footnote ⁹⁷ Initial development was carried out in collaboration with Mullard at Mitcham and STC at Harlow. Progress at Mullard was considered ‘disappointing’ by CVD.Footnote ⁹⁸ Moreover, SERL's expertise was considered to be ‘well ahead of that in Industry’ and by 1976 had ‘shown a definite single route towards the manufacture of satisfactory GaAs photocathodes’, and so ‘the extramural programme on alternative methods [was] discontinued’.Footnote ⁹⁹

The situation was reported to the CVD Technical Committee in June 1977: ‘Recent success on GaAs photocathode devices at Baldock has led to a review of the likely applications, and a decision will be taken in the near future on whether to proceed to development and if so, on what format.’Footnote ¹⁰⁰ SERL (which in 1976 merged with RRE to form RSRE) now had ‘a preferred manufacturing method using hetero-epitaxial layers of GaAs and GaAlAs bonded in glass, which also gives the required high sensitivity’. This was initially done using liquid phase growth, but work continued on ‘vapour phase growth using metal alkyls which offer the possibility of better layers’.Footnote ¹⁰¹

When the decision was made by the MoD to initiate photocathode production, an industrial contractor was required, but neither Mullard nor STC was prepared to take the step into commercial production.Footnote ¹⁰² Instead, EEV (English Electric Valve) of Chelmsford won the contract for photocathode production. EEV had experience in producing image-intensifying equipment (they were RRE's main industrial partner in the development of infrared imaging pyroelectric technologyFootnote ¹⁰³), but had no track record in epitaxial growth techniques, which was the key to the photocathode. However, the SERL/RSRE team was confident that it could transfer the technology into EEV in order to meet the MoD's procurement requirements. This led to the development of night goggles that went into service in the mid-1980s and were used in the first Gulf War.Footnote ¹⁰⁴ This work was carried out so successfully that RSRE and EEV were joint recipients of a Queen's Award in 1987, but this award proved a poor guide to longer-term technological performance. According to one account, changes in EEV's management resulted in a requirement for technical managers to rotate jobs so as to broaden their experience, with the consequence in practice that the specific skills and knowledge base necessary for photocathode production were eroded.Footnote ¹⁰⁵ EEV (now E²V) continues to be a major producer of image sensors for defence and other specialist applications, but using silicon-based CCD (charge coupled devices) or CMOS (complementary metal oxide semiconductor) technologies.Footnote ¹⁰⁶

As SERL gained confidence in the MOCVD technique it also sought to apply it to laser production, its other big opto-electronic application of III–Vs. Laser action in GaAs had first been demonstrated in the USA in 1962.Footnote ¹⁰⁷ CVD funding for research on GaAs lasers was focused at STL where the development of fibre optics for telecommunications was pioneered in the 1960s. Amongst the contracts given to firms and universities to work on this topic was one to develop high-power GaAs lasers placed with STC/STL in 1966.Footnote ¹⁰⁸ The following year, the availability of devices from STC led SERL to cease its in-house work on GaAs lasers, though SERL continued to monitor and support extramural work at STL through CVD contracts.Footnote ¹⁰⁹

A familiar complaint of CVD concerned the reluctance of STL (which was owned by the US ITT corporation) to move into production, as the CVD Technical Committee noted in December 1970:

However, the following July, CVD were informed that ‘STL were setting up a pilot production facility as part of the development programme and this should satisfy demands until it grew to a size that would tempt the ITT organisation to take it into one of its production facilities’.Footnote ¹¹¹ Moreover, it was concluded that the ‘policy of concentrating all the CVD funding on semiconductor lasers at STL appears to be paying off with performance data somewhat better than those obtained in the USA’.Footnote ¹¹² By 1975, ‘STL had set up a unit at Paignton for the production of GaAs lasers and were selling mostly in the export market’.Footnote ¹¹³

RSRE's success with MOCVD-produced photocathodes then led them to apply the same approach to lasers in the late 1970s: ‘we said, well, we haven't finished there, this is a generic technology’.Footnote ¹¹⁴ This required a more complex structure than that used in the photocathode, with more junctions and much more precise control of layer thickness. Once mastered, however, lasers produced by MOCVD offered better performance than previously possible.

The new levels of efficiency achieved in these devices stemmed from the application of ‘low-dimensional structures’ (LDS) physics.Footnote ¹¹⁵ LDS takes advantage of the ability to build up precisely (one atomic plain at a time) the epitaxial layers in a crystal structure while mixing gallium arsenide and aluminium arsenide layers without disrupting the structure (because they have the same lattice spacing). This means that the semiconductor properties can be very precisely controlled, and in LDS this manipulation extends to the use of crystal structures with wavelengths shorter than an electron wavelength. This allows electronic activity to be restricted to two dimensions within an epitaxial layer, providing even more precise control over semiconductor properties.

RSRE's collaboration with STC (at both Harlow and Paignton) on MOCVD technology led to a Queen's Award for Technology in 1991. Commercial exploitation was aided by British Telecom support for STC research which led to worldwide application of MOCVD in communications technology. STC Optical Devices at Paignton was first taken over by Nortel (with major job losses following), then by Bookham Technology, which itself merged with Avanex to form Oclaro.Footnote ¹¹⁶ Paignton now operates as a research facility with MOCVD being used for laser manufacturing being carried out at Caswell, also now owned by Oclaro.Footnote ¹¹⁷

In addition to companies using the technology in device production, other UK companies became suppliers of the production technology itself. MOCVD reactors based on Sidney Bass's original design were produced and sold by EEV, Thomas Swann and Cambridge Instruments (although the last of these preferred the term metal organic vapour phase epitaxy or MOVPE).Footnote ¹¹⁸ RSRE research also led to the development of a reactor sold by EEV that was capable of growing narrow band-gap II–VI materials such as cadmium mercury telluride, used in high-quality infrared vision systems.Footnote ¹¹⁹

A further spin-off from work at RSRE centred on the source materials used in the MOCVD process, such as trimethyl gallium and trimethyl aluminium. Very high levels of purity (better than one part per million) are required for these precursors if the semiconductor properties are not to be degraded. Two early UK producers of such materials, BDH Chemicals Ltd and Mining and Chemical Products Ltd, both licensed technology via the NRDC.Footnote ¹²⁰ Other work resulting from collaboration between RSRE and teams at Liverpool University and Queen Mary College in London was taken up by a new company, EPICHEM, founded in 1983 with the help of the Merseyside Development Corporation.Footnote ¹²¹

The other area of epitaxial technology to which the UK defence establishments made a significant contribution was molecular beam epitaxy (MBE). MBE is carried out in a very high vacuum, providing a very precise process for research purposes, although initially the high expense and low throughput limited its suitability for mass production.Footnote ¹²² UK work on MBE was stimulated by the formation in 1983 of an MBE Working Party within the Gallium Arsenide Consortium.Footnote ¹²³ This interest created a market for MBE reactors which was met by Vacuum Generators Ltd (later VG Semicon), which along with collaboration between the company and RSRE led to VG Semicon becoming a major world supplier of MBE equipment.Footnote ¹²⁴