title: Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane.
abstract: We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gate-defined quantum dots in Si/SiGe heterostructures were formed on top of strain-graded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.
authors.affiliation: Wisconsin Institute for Quantum Information, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706-1390, USA. Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706-1390, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Knapp
authors.forename: R T
authors.initials: RT
authors.lastname: Mohr
authors.forename: Yize Stephanie
authors.initials: YS
authors.lastname: Li
authors.forename: Brandur
authors.initials: B
authors.lastname: Thorgrimsson
authors.forename: Ryan H
authors.initials: RH
authors.lastname: Foote
authors.forename: Xian
authors.initials: X
authors.lastname: Wu
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ward
authors.forename: D E
authors.initials: DE
authors.lastname: Savage
authors.forename: M G
authors.initials: MG
authors.lastname: Lagally
authors.forename: Mark
authors.initials: M
authors.lastname: Friesen
authors.forename: S N
authors.initials: SN
authors.lastname: Coppersmith
authors.forename: M A
authors.initials: MA
authors.lastname: Eriksson