Magnetic depopulation of subbands and universal conductance fluctuations in quasi-one dimensional GaAsAlGaAs heterostructures

✍ Scribed by H. van Houten; B.J. van Wees; J.E. Mooij; G. Roos; K.-F. Berggren

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 444 KB
• Volume: 3
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1016/0749-6036(87)90231-x

✦ Synopsis

Narrow conducting channels have been fabricated in the two dimensional electron gas in a GaAs-AlGaAs heterostructure, using a recently developed shallow mesa etch technique. Four terminal high field magnetoresistance measurements at temperatures down to 2 K have been performed on samples with etched width between 8 pm and 0.5 pm. The Shubnikov-de Haas oscillations are studied, and clear evidence is presented for magnetic depopulation of l-dimensional subbands. The data for the 0.5 pm wide channel are in satisfactory agreement with a simple analysis based on a parabolic confinement potential. Large sidewall depletion effects are found, in agreement with our recent analysis of the weak field negative magnetoresistance. We also observe irregular structure in the magnetoresistance. The dependence of the effects on the orientation of the magnetic field shows that the magnetoresistance arises from the orbital motion of the 2-dimensional electrons. The magnitude and typical field scales of the aperiodic structure are in agreement with predictions based on the theory of universal conductance fluctuations.