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SUMMARY:Undoped 2D Electron systems as a tool  for optimising MBE growth (
 SP Workshop) - Mr Ben Ramsay\, University of Cambridge\, Semiconductor Phy
 sics Group
DTSTART:20160511T131500Z
DTEND:20160511T141500Z
UID:TALK64324@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:The MBE growth of ultra-high-quality GaAs/AlGaAs epilayer stru
 ctures has enabled the discovery of many novel physical phenomena\, for ex
 ample the fractional quantum Hall effect (FQHE) in two- dimensional electr
 on systems (2DESs). In order to attain the highest electron mobilities (in
  excess of 107 cm2V-1s-1)\, it is necessary to understand and limit the do
 minant sources of disorder during the wafer growth. These include both int
 entional (i.e. doping) and unintentional charged impurities\, interface ro
 ughness and surface defect states\, all of which cause electron scattering
 . \n\nThe electron mobility in a modulation-doped 2DES is dominated by dop
 ing impurities. By contrast the electron mobility in an undoped is dominat
 ed by unintentional background impurities and interface roughness. By meas
 urement and numerical modelling of the mobility versus density characteris
 tics of an undoped wafer\, it is possible to determine the concentration o
 f background impurities and the characteristic length and height scales of
  the roughness. Therefore these systems are a powerful tool for assessment
  of the cleanliness of an MBE chamber and optimisation of growth condition
 s. \n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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