Oral history of British science
Hilsum, Cyril (Part 12 of 25)
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Interviewee's home, Middlesex
Hilsum, Cyril, 1925- (speaker, male)
Lean, Thomas (speaker, male)
Part 12 [1:20:05] Description of how a semiconductor works: controllable conductivity by adding impurities; pure semiconductors not conducting at room temperatures; [02:30 pause] conductivity through a sea of electrons, movement of electrons and holes made by removed electrons; n, or negative type, semiconductors where electrons move; p type electrons where the electron hole moves; effects at n-p junction the basis for useful properties of semiconductors; ability to control passage of electrons and holes with electric fields, ability to cut off current the basis of computer chips. [06:00] Comments on semiconductor laser: previous laser use of light amplified within gas or crystal; creation of light by semiconductor by spontaneous emission; process of stimulated emission in semiconductor allowing amplification of light; use of p-n junction to create light emitting device, arrangements to build up light in a narrow wavelength emission; [10:20] 1960s work by French and Russian groups on semi-conductor laser, idea of forming a resonant cavity to amplify a single frequency, Bob Hall's implementation of idea at General Electric Schenectady in 1962 with a cube of gallium arsenide; ways of preventing energy loss inherent to cube of gallium arsenide; IBM's Marshall Nathan and General Electric's Nick Holonyak building semiconductor lasers shortly after Bob Hall in 1962; [16:10] MIT Lincoln laboratory construction of laser; Baldock production of first semiconductor laser outside USA in December 1962. [17:10] Comments on: reasons for wanting to build semiconductor injection laser; use of lasers in many applications; lower purity of semiconductor lasers compared to gas lasers; few applications in mind at the start, making a laser because others already had; finding uses for lasers, burning paint, army labs at Christchurch's interest in use of laser in communications. [21:10] Description of making semiconductor laser: preparing gallium arsenide by diffusing Zinc into it; adding contacts; creation of mirrored surfaces by cleaving gallium arsenide with a razor blade; apparatus around gallium arsenide sample. [24:50] Remarks on: knowledge of other projects from other laboratories sending them preprints of articles; accuracy required for mirrored surfaces; description of semiconductor laser set up, tiny size of gallium arsenide chip, cooling arrangements; different individuals involved with different parts of making laser; motivation of knowing it could be done; [31:40] Comments on the semiconductor laser and the press: demonstrating laser for David Fishlock of 'New Scientist'; anecdote about CH's response to journalists at a physics exhibition, where the laser was being demonstrated, and reactions from boss Robert Sutton and Alusuisse suppliers. [37:35] Further comments on semiconductor laser: applications for semiconductor laser initially limited due to need for cooling; work of groups in Leningrad and Bell Labs on more complex p-n junctions. [39:40] Comments on continuing work trying to get microwave radiation out of semiconductors: Ian Gunn's work in the USA on gallium arsenide, using bouncing ball technique to quickly generate pulses, acoustic wave amplification, discovery of fast pulses from gallium arsenide at high fields, Gunn's ruling out of CH, Tom Watkins and Brian Ridley explanations. [43:35] Comments on controversy over Gunn's disbelief of work of other Britons: IBM and Bell Labs enmity; Herb Kroemer's letter supporting CH, Watkins, Ridley interpretation, and bringing in Ridley's work on domains; naming of Gunn-Diode and Ridley-Watkins-Hilsum [RWH] mechanism; long lasting enmity, eventual Bell paper proving Ridley-Watkins-Hilsum explanation; anecdote about CH talk at a 1970s conference in Denton when IBM physicist Peter Price was lambasted by audience over the issue; curiosity over IBM's actions over issues. [54:00] Comments on: transferred electron device and semi-conductor laser justifying research on gallium arsenide; widening of semiconductor research into new fields; personally satisfyng period of work to CH; semi-insulating gallium arsenide's value as a non-conductive substrate in growing semiconductor layers in vapour phase; [1:00:00] use of semi-insulating gallium arsenide as base for circuits today; reluctance of patent agents at Admiralty; CH growing reputation in 1964, invited talk at international conference on semiconductors; anecdote about lavish entertainment in Orangerie at conference in France, despite de Gaulle forbidding use of Versailles Hall of Mirrors as conference wasn't in French; [1:06:30] changing place of silicon to substance being used for making devices as it became better understood, anecdote about Alan Gibson predicting in 1962 that no further conferences on silicon would be necessary in future. [1:08:15] Comments on troubles at SERL Baldock: good progress all round, John Allen's work following up Birmingham University research on gallium phosphide making red LEDs; Boss Robert Sutton's disapproval of semi-conductor group's progress and limited understanding of semiconductor physicists; other groups working on topics closer to defence application, such as production of radar components and ring laser for submarine navigation; Sutton giving CH group to a different manager and pushing CH out of SERL; organisational arrangements in Sutton's favour; CH old group assigned to lesser task of making film markers for TSR2 aircraft; [1:14:35] anecdote about CH managing visitor from Bell labs; Sutton pushing out Oliver Simpson, who left to NPL and become Home Office chief scientist; Christopher Rose-Innes and Emlyn Rhoderick leaving to UMIST at Manchester; senior solid state staff all leaving apart from John Allen; CH search for a new post at NPL and Malvern, CH replacing Alan Gibson at Malvern; anecdote about CH children's hostile reaction to moving to Malvern and disruption of wife's career; Sutton connection to CVD through Paul Wright.
Interview with physicist, Cyril Hilsum