Magneto-transport of an electron bilayer system in an undoped Si/SiGe double-quantum-well heterostructure

We report the design, the fabrication, and the magneto-transport study of an electron bilayer system embedded in an undoped Si/SiGe double-quantum-well heterostructure. Combined Hall densities (nHall) ranging from 2.6-×-1010-cm-2 to 2.7-×-1011-cm-2 were achieved, yielding a maximal combined Hall mobility (μHall) of 7.7-×-105-cm2/(V · s) at the highest density. Simultaneous electron population of both quantum wells is clearly observed through a Hall mobility drop as the Hall density is increased to nHall > 3.3-×-1010-cm-2, consistent with Schrödinger-Poisson simulations. The integer and fractional quantum Hall effects are observed in the device, and single-layer behavior is observed when both layers have comparable densities, either due to spontaneous interlayer coherence or to the symmetric-antisymmetric gap.