CPM Seminar

The role of MBE in low dimensional physics

Loren Pfeiffer

Bell Laboratories
Lucent Technologies Inc.

Much of the progress in the physics of lower dimensional electron systems over the past 25 years has depended on the continuous improvement of the 2D carrier mobility at the MBE semiconductor heterojunction. Beginning with the first report of modulation-doping of GaAs quantum wells in 1978 by Störmer, Gossard, and Dingle, the electron mobility for such 2D systems has increased from the GaAs bulk value by nearly four orders of magnitude to our current record 3.1x10⁷ cm²/Vsec at 0.3K. These results, the best for any semiconductor hetero-interface, imply a ballistic mean-free-path for GaAs conduction electrons in excess of 300 μm, and a mean time between scattering events in excess of 3 nsec. Our experience suggests that the GaAs/AlAs hetero-interface is among the most perfect in all of nature, and as such it has become a valuable laboratory for studies of all manner of subtle effects in condensed matter physics. We will review several recent experiments where high sample mobility has directly led to the discovery of new physics, and we will discuss new work on extending the concept of mobility to neutral excitons.