Quantum anti-dot formed with an airbridge gate in the quantum Hall regime

Abstract

We demonstrate a quantum antidot (QAD) formed with an airbridge gate on an AlGaAs/GaAs heterostructure, where a sub-micron pillar-shaped surface gate is biased via the bridge. We study transport through the QAD in the two regimes; one with a fully depleted region and the other with a partially depleted region at the center of the QAD. While standard Coulomb blockade (CB) oscillations with discrete levels are observed in the fully depleted region, short-period CB oscillations and more complicated patterns with multiple QADs are seen in the partially depleted region. The device is promising for investigating the few-particle regime.

Sensitive current measurement on a quantum antidot with a Corbino-type electrode

“…This implies that the electrons under the pillar are not fully depleted. 21) In this case, the orbital diameter might deviate from the above estimate. This partially depleted region should be investigated further.…”

“…20) A submicron pillar gate with airbridge wiring is promising for trapping a small number of particles in a QAD. 21) Another technical issue we tackle in this work is the measurement scheme. Previous measurements on QADs have been carried out indirectly by observing deviation from the quantized Hall resistance or the vanished longitudinal resistance.…”

“…The side gate (the blue pentagon) is used to form a current path from the inner electrode of the Corbino disk. The whole gate structure is fabricated by depositing Ti (30 nm) and Au (270 nm) layers on a triple layer resist [ZEP (150 nm), PMGI (500 nm), and ZEP (250 nm) from the bottom] patterned by electron-beam lithography, 21,25) as shown in the cross section of Fig. 2(b) and the scanning electron micrograph (SEM) of Fig.…”