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SUMMARY:Cryogenic on-chip multiplexer for the statistical study of quantum
  transport in low dimensional devices - Mr. Haider Al-Taie\, SP Group\, Ca
 vendish Laboratory\, Cambridge
DTSTART:20141124T141500Z
DTEND:20141124T151500Z
UID:TALK55843@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:This seminar describes the development and implementation of a
  cryogenic on-chip multiplexer which significantly increases the number of
  quantum devices measured on a single chip. It is demonstrated to contact 
 an array of 256 (16 x 16) split-gate transistors\, where each device is in
 dividually measureable\, using only 19 electrical contacts. Split-gate tra
 nsistors form one-dimensional channels in a two-dimensional electron gas (
 2DEG) formed in a GaAs/AlGaAs heterostructure. The implementation of the m
 ultiplexer does not require the modification of existing fabrication or ex
 perimental set-ups. The compatibility of the multiplexer with existing app
 aratus allows for easy integration into current research. This provides a 
 major multiplication in the effectiveness of research. This enables new ex
 periments to study yield\, reproducibility and statistics of electrical pr
 operties.\n\nThe yield\, reproducibility\, spatial variations and statisti
 cal analyses of particular electrical characteristics which exist in split
 -gate transistors are presented. These studies are important in the area o
 f quantum electronics. At low temperatures\, split gates exhibit quantisat
 ion of conductance in units of 2e2/h. A ‘quantum yield’ (based on the 
 behaviour of the device) was defined which increases from 55% to 86% when 
 illuminating the split-gate devices with a light emitting diode (LED). Cor
 relations and spatial variations of electrical properties are investigated
  upon illumination and a second cooldown. Techniques to quantify the varia
 tion in electrical properties\, due to short-scale variations in electron 
 density (which limit reproducibility from device-to-device)\, of the wafer
  are presented.
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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