Quantum hall effect in wide parabolic GaAs/Al xGa 1−xAs wells

Abstract

Parabolic well structures have been proposed to produce thick spatially uniform regions of dense high mobility electron gas. Wide parabolic GaAs/Al xGa 1−xAs wells were fabricated using molecular beam epitaxy by grading the average Al concentration. These structures have high mobility at low temperatures (μ = 5 × 10 4 to 2.5 × 10 5 cm 2/V sec) and show the integer and fractional quantum Hall effect. Characteristic changes in the integer quantum Hall effect and the longitudinal magnetoresistance in a 4000 Å wide well are measured as the well is partially filled with electrons using persistent photoconductivity. These data establish that up to three electric subbands of the well are occupied.