Single-hole transistor in p-type GaAs∕AlGaAs heterostructures

Grbić, Boris; Leturcq, R.; Ensslin, Klaus; Reuter, D.; Wieck, A. D.

doi:10.1063/1.2139994

Cited by 43 publications

(48 citation statements)

References 13 publications

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“…No Fourier transform is required to verify this effect. As additional evidence we directly measure a beating of the h/2e oscillations and a pronounced and persistent zero field magnetoresistance minimum due to destructive interference of time-reversed paths.The sample was fabricated by atomic force microscope (AFM) oxidation lithography on a p-type carbon doped (100) GaAs heterostructure, with a shallow twodimensional hole gas (2DHG) located 45 nm below the surface [18]. An AFM micrograph of the ring structure is shown in the inset of Fig.…”

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Aharonov-Bohm Oscillations in the Presence of Strong Spin-Orbit Interactions

et al. 2007

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We have measured highly visible Aharonov-Bohm (AB) oscillations in a ring structure defined by local anodic oxidation on a p-type GaAs heterostructure with strong spin-orbit interactions. Clear beating patterns observed in the raw data can be interpreted in terms of a spin geometric phase. Besides h/e oscillations, we resolve the contributions from the second harmonic of AB oscillations and also find a beating in these h/2e oscillations. A resistance minimum at B = 0 T, present in all gate configurations, is the signature of destructive interference of the spins propagating along time-reversed paths.Interference phenomena with particles have challenged physicists since the foundation of quantum mechanics. A charged particle traversing a ring-like mesoscopic structure in the presence of an external magnetic flux Φ acquires a quantum mechanical phase. The interference phenomenon based on this phase is known as the Aharonov-Bohm (AB) effect [1], and manifests itself in oscillations of the resistance of the mesoscopic ring with a period of Φ 0 = h/e, where Φ 0 is the flux quantum. The Aharonov-Bohm phase was later recognized as a special case of the geometric phase [2,3] acquired by the orbital wave function of a charged particle encircling a magnetic flux line.The particle's spin can acquire an additional geometric phase in systems with spin-orbit interactions (SOI) [4,5,6]. The investigation of this spin-orbit (SO) induced phase in a solid-state environment is currently the subject of intensive experimental work [7,8,9,10,11,12]. The common point of these experiments is the investigation of electronic transport in ring-like structures defined on two-dimensional (2D) semiconducting systems with strong SOI. Electrons in InAs were investigated in a ring sample with time dependent fluctuations [7], as well as in a ring side coupled to a wire [9]. An experiment on holes in GaAs [8] showed B-periodic oscillations with a relative amplitude ∆R/R < 10 −3 . These observations [7,8] were analyzed with Fourier transforms and interpreted as a manifestation of Berry's phase. Further studies on electrons in a HgTe ring [10] and in an InGaAs ring network [11] were discussed in the framework of the AharonovCasher effect.In systems with strong SOI, an inhomogeneous, momentum dependent intrinsic magnetic field B int , perpendicular to the particle's momentum, is present in the reference frame of the moving carrier [13]. The total magnetic field seen by the carrier is therefore B tot = B ext + B int , where B ext is the external magnetic field perpendicular to the 2D system and B int is the intrinsic magnetic field in the plane of the 2D system present in the moving reference frame (right inset Fig. 1(a)). The particle's spin precesses around B tot and accumulates an additional geometric phase upon cyclic evolution.Effects of the geometric phases are most prominently expressed in the adiabatic limit, when the precession frequency of the spin around the local field B tot is much faster than the orbital frequency of the charged particl...

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Aharonov-Bohm Oscillations in the Presence of Strong Spin-Orbit Interactions

et al. 2007

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“…Therefore this shallow 2DHG offers the possibility to fabricate new types of spinbased quantum devices with the technique of local oxidation using an atomic force microscope [2,[10][11][12]. …”

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“…We report on magnetoresistance measurements on a two-dimensional hole gas (2DHG) created 45 nm below the surface of a C-doped GaAs/AlGaAs heterostructure. We observe the following three signatures of strong SO interactions: a beating in the Shubnikov-de Haas oscillations, a classical Lorentzian positive magnetoresistance due to the presence of the two spin-split subbands and a weak anti-localization dip in the magnetoresistance.The Hall-bar is fabricated from a 2DHG located 45 nm below the surface [2]. The Hall-bar is W ¼ 100 mm wide, and the separation between the contacts used for the measurements of the longitudinal resistance is either L ¼ 500 mm.…”

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Strong spin–orbit interactions in carbon doped p-type GaAs heterostructures

Grbić¹,

Leturcq²,

Ihn³

et al. 2008

Physica E: Low-dimensional Systems and Nanostructures

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“…The extent of the depletion depends critically on the depth of the 2D gas and hence the need to grow very shallow 2D samples as described above [8]. Recently, this technique was used to pattern mesoscopic structures in GaAs 2DHSs [9,10,11]. Similar to these techniques, in order to deplete the carriers in our structures, we used a tip voltage of −27.5 V, a humidity level of ∼ 50% and a scanning speed of 0.05 µm/s.…”

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Strong Aharonov-Bohm oscillations in GaAs two-dimensional holes

Habib

Tutuc

Shayegan

2007

Applied Physics Letters

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We measured Aharonov-Bohm resistance oscillations in a shallow two-dimensional GaAs hole ring structure, defined by local anodic surface oxidation. The amplitude of the oscillations is about 10% of the ring resistance, the strongest seen in a hole system. In addition we observe resistance oscillations as a function of front gate bias at zero magnetic field. We discuss the results in light of spin interference in the ring and possible applications to spintronics.The Aharonov-Bohm (AB) effect and related phenomenon in mesoscopic semiconductor structures have attracted much attention over the last years. The AB effect reflects the fact that when magnetic flux pierces through a ring structure, a phase difference develops between the electron wavefunctions traveling in the ring's two arms [1]. This phase difference is 2π(Φ/Φ 0 ), where Φ = πr 2 B is the magnetic flux through the ring, r is the ring radius, B is the applied magnetic field in the perpendicular direction, and Φ 0 = h/e is the flux quantum. Hence the resistance of the ring exhibits oscillations periodic in B with a period equal to πr 2 /(h/e).In semiconductors, the AB effect has been seen in rings made from two-dimensional (2D) electron systems in various materials [2] but has been difficult to observe in 2D hole systems (2DHSs). Recently, AB oscillations with an amplitude of about 0.1% (of the total ring resistance) were observed by Yau et al.[3] in a 500 nm radius ring structure patterned via electron-beam lithography in GaAs 2D holes. In the present work we aimed to increase the amplitude of the AB oscillations in this system by fabricating smaller rings [4]. For this purpose we employed the local anodic oxidation (LAO) technique using an atomic force microscope (AFM). Here we present our measurements of AB oscillations in a GaAs 2D hole sample with r ≃ 160 nm. The observed AB oscillation amplitude is about 100 times larger than in Ref. [3]. A further motivation for our experiments is the fact that the 2DHS in GaAs exhibits strong spin-orbit interaction which is tunable with gate bias [5]. Nitta et al. [6] highlighted that the resistance in a ring structure in such a system can be modulated by changing the gate bias even at B = 0 and proposed it as a spin interference device. In our ring structure, we do indeed observe oscillations as a function of gate bias at B = 0; however, the origin of these oscillations is unclear.Our sample was grown on a GaAs (311)A substrate by molecular beam epitaxy and contains a modulationdoped 2DHS confined to a GaAs/Al 0.3 Ga 0.7 As interface. The interface is separated from an 11 nm-thick Si-doped Al 0.3 Ga 0.7 As layer (Si concentration of 1.64 × 10 19 cm −3 ) by a 15 nm Al 0.3 Ga 0.7 As spacer layer. A 5 nm GaAs layer caps the structure resulting in the 2D hole layer residing ≃ 31 nm below the surface. We fabricated Hall bar samples via optical lithography and used alloyed In/Zn for the ohmic contacts. Metal gates were deposited on the sample's front and back to control the 2D hole density (p). Before patterning the s...

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Single-hole transistor in p-type GaAs∕AlGaAs heterostructures

Cited by 43 publications

References 13 publications

Aharonov-Bohm Oscillations in the Presence of Strong Spin-Orbit Interactions

Aharonov-Bohm Oscillations in the Presence of Strong Spin-Orbit Interactions

Strong spin–orbit interactions in carbon doped p-type GaAs heterostructures

Strong Aharonov-Bohm oscillations in GaAs two-dimensional holes

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