Ballistic transport in a GaAs/AlxGa1−xAs one-dimensional channel fabricated using an atomic force microscope

Abstract

We fabricate a one-dimensional constriction in a shallow, δ-doped GaAs/AlxGa1−xAs two-dimensional electron gas, by locally oxidizing the surface using an atomic force microscope. The channel exhibits ballistic conduction with up to seven conductance plateaus, quantized in units of 2e2/h. The dependence of the device conductance on dc bias voltage reveals the energy separation of the first two subbands to be ΔE1,2=5.5(±0.3) meV, which allows ballistic conduction to be observed up to a temperature of 20 K. A lateral electric field, combined with the hard-walled confinement due to the insulating lines, allows manipulation of the electron wave function in a way which is not possible with surface-gated devices.

Invited Review Electronic properties of nanostructures defined in Ga[Al]As heterostructures by local oxidation

“…Very recently, other groups have started to implement this lithographic technique [12,26,27]. It will be exciting to watch the evolution of local oxidation over the next few years.…”

“…the distance between surface and 2DEG is smaller than about 50 nm. Several other groups have also fabricated highquality nanostructures using this method [26,27]. In the present review, we describe this patterning technique (referred to as local oxidation (LO) in the following) in detail and characterize the electronic properties of the resulting confinement.…”

Energy spectroscopy of controlled coupled quantum-wire states

“…Spatial 1D constrictions are formed of the order of the Fermi wavelength l F ∼ 35 nm and much below the mean free path length of l ∼ 10 μm as achieved in high-electron-mobility (∼1 × 10 6 cm 2 V −1 s −1 ) 2DEGs in AlGaAs/GaAs heterostructures. Various techniques can be used, such as metal-deposited split gates 16,17 , etching 18-20 or local anodic oxidation 21 . Conductance quantization 16,17 in linear and nonlinear transport is reported for etched single EWGs for temperatures up to 30 K (ref.…”

Invited Review Nanoscale devices fabricated by dynamic ploughing with an atomic force microscope

“…However, an oxide penetration of 5-10 nm at a line width of 200 nm indicates that local oxidation can be regarded as a well-controlled particularly shallow etching, which enables one to isolate the 2DEG provided its distance from the surface is less than about 50 nm [40]. In QPCs fabricated by local oxidation the highest separation reported so far is E 1,2 ≈ 5.5 meV, where the distance between surface and 2DEG is only 28 nm [37]. Due to a much larger depth-to-width ratio this restriction is absent if the barriers are induced by wet-etched grooves.…”

“…Particularly gentle is the potential forming by means of split-gate electrodes [33][34][35]. Electric isolation with little damage is also achieved by local anodic oxidation with the biased tip of an AFM, which can be combined with in-plane gates or a top gate [36,37]. The third particularly low-damage method is wet etching for depleting the 2DEG beneath the recesses, followed by depositing a metal top gate which covers the constriction and the surrounding reservoirs [23,38,39].…”