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SUMMARY:Carrier lifetimes in high-lifetime silicon wafers and irradiation 
 induced recombination centres
DTSTART;VALUE=DATE-TIME:20220901T132000Z
DTEND;VALUE=DATE-TIME:20220901T134000Z
DTSTAMP;VALUE=DATE-TIME:20220826T121708Z
UID:indico-contribution-3637@indico.stfc.ac.uk
DESCRIPTION:Speakers: Koji Yokoyama (ISIS\, STFC\, UK)\nPhotoexcited muon 
 spin spectroscopy (photo-$\\mu$SR) was used to measure excess charge carri
 er lifetimes in passivated silicon wafers. Optically generated excess carr
 iers interact with muonium centres via carrier exchange interaction and in
 duce relaxation in the $\\mu$SR time spectrum. The photo-$\\mu$SR techniqu
 e utilises this additional relaxation rate as a measure of the excess carr
 ier density\, which in turn enables us to measure carrier lifetime spectra
  by controlling delays between a muon and laser pulse $[1]$. In addition\,
  the depth-resolved measurement can characterise carrier kinetics at speci
 fic depths within a Si wafer and enables us to separate bulk and surface r
 ecombination rates $[2]$. Based on these developments\, we recently applie
 d the technique to passivated Si samples with extremely long effective lif
 etimes ($>$1 ms) and observed that prolonged muon irradiation resulted in 
 significant degradation of a measured lifetime $[3]$. Follow-up characteri
 sation measurements\, including deep-level transient spectroscopy\, strong
 ly suggested that beam damage generated defect-related recombination centr
 es in bulk. Our results demonstrate an extremely rare case in $\\mu$SR app
 lications\, where beam damage to crystalline lattice was clearly detected 
 by virtue of high-lifetime Si wafers and\, in turn\, low native defect den
 sities. \n$[1]$ K. Yokoyama\, et al. Phys. Rev. Lett. 119\, 226601 (2017)\
 ; Appl. Phys. Lett. 115\, 112101 (2019).\n$[2]$ K. Yokoyama\, et al. Appl.
  Phys. Lett. 118\, 252105 (2021).\n$[3]$ J. D. Murphy\, et al. submitted t
 o Journal of Applied Physics.\n\n![A series of repeat lifetime measurement
 s were performed on a HfO$_2$ passivated Si sample. (a): Effective carrier
  lifetimes were measured as a function of beam exposure time. (b): A photo
 luminescence lifetime image was taken on the sample (5$\\times$5 cm$^2$) a
 fter the muon experiment. White parts closer to the edges indicate longer 
 carrier lifetimes. The central black spot with shorter lifetimes correspon
 ds to a region exposed to muon beams.][1]\n  [1]: https://ucc98303ba1c74bf
 870642bd8ca6.previews.dropboxusercontent.com/p/thumb/ABmahQ2Y1qE6orS1BxHIE
 1m2IMRHSMAYbvvHU97P-ItKYc4-NMbqPZVl2ucnv0Ac_6butSqCkTtb0wlfrXwga1KEFkenCxZ
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 X-aQ3i8BSrc5PbytV-sRl3xKUfFVNSUO8l9RynS_8qZQA58DKUldaeeEb-55-UzJbE2gJvEU9v
 DnrrdqngaxbaKA2saPdSrDfExQ-ZCky8RWU2x-A/p.jpeg\n\nhttps://indico.stfc.ac.u
 k/event/53/contributions/3637/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3637/
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