We report on fabrication of two-dimensional electrons in AlAs quantum wells with mobilities up to 31 m2/Vs. Magnetoresistance measurements reveal fractional quantum Hall states at high-order filling factors, and up to v = 11/3. Shubnikov-de Haas oscillations of high-density samples suggest that electrons occupy two X-point valleys. We also study properties of hysteretic resistance spikes occurring at transitions between quantum Hall ferromagnets in AlAs quantum wells, and show that the spike hysteresis depends sensitively on the number of occupied energy levels involved in the transition.
All Science Journal Classification (ASJC) codes
- Statistical and Nonlinear Physics
- Condensed Matter Physics