MBE Growth of Strained HgTe/CdTe Topological Insulator Structures

Ballet, P.; Thomas, Candice; Baudry, Xavier; Bouvier, Clément; Crauste, O.; Meunier, Tristan; Badano, G.; Veillerot, M.; Barnes, Jean‐Paul; Jouneau, Pierre‐Henri; Lévy, Laurent

doi:10.1007/s11664-014-3160-z

Cited by 20 publications

(13 citation statements)

References 17 publications

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“…INTRODUCTION The physics of relativistic Dirac fermions in semiconductors has recently moved into the focus of modern research, due to their unique properties and promising novel applications, for recent reviews see [1][2][3][4][5][6] . Among diverse systems addressed in the literature HgTe-based structures represent an extraordinary material class, allowing the fabrication of a high quality material [7][8][9][10][11][12] with Dirac-like systems of different forms. The latter includes topological protected edge and surface states of twoand three-dimensional topological insulators [13][14][15][16][17][18][19][20][21][22][23][24][25][26] , QWs with critical thickness 13,[27][28][29][30][31][32][33][34] and bulk HgCdTe material at the point of semiconductor-to-semimetal transition 35 .…”

Section: Pacs Numbersmentioning

confidence: 99%

Cyclotron-resonance-assisted photocurrents in surface states of a three-dimensional topological insulator based on a strained high-mobility HgTe film

et al. 2015

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We report on the observation of cyclotron resonance induced photocurrents, excited by continuous wave terahertz radiation, in a 3D topological insulator (TI) based on an 80 nm strained HgTe film. The analysis of the photocurrent formation is supported by complimentary measurements of magneto-transport and radiation transmission. We demonstrate that the photocurrent is generated in the topologically protected surface states. Studying the resonance response in a gated sample we examined the behavior of the photocurrent, which enables us to extract the mobility and the cyclotron mass as a function of the Fermi energy. For high gate voltages we also detected cyclotron resonance (CR) of bulk carriers, with a mass about two times larger than that obtained for the surface states. The origin of the CR assisted photocurrent is discussed in terms of asymmetric scattering of TI surface carriers in the momentum space. Furthermore, we show that studying the photocurrent in gated samples provides a sensitive method to probe the effective masses and the mobility of 2D Dirac surface states, when the Fermi level lies in the bulk energy gap or even in the conduction band.

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Section: Pacs Numbersmentioning

confidence: 99%

Cyclotron-resonance-assisted photocurrents in surface states of a three-dimensional topological insulator based on a strained high-mobility HgTe film

et al. 2015

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“…Particular attention to lower the defects present in the HgTe layer and to obtain sharp HgTe / Hg 0.3 Cd 0.7 Te interfaces was paid during the structure growth [15] (see Fig.1 (b)). Two different structures with similar thickness were grown and gave very similar results.…”

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confidence: 99%

Revealing topological Dirac fermions at the surface of strained HgTe thin films via quantum Hall transport spectroscopy

et al. 2017

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We demonstrate evidences of electronic transport via topological Dirac surface states in a thin film of strained HgTe. At high perpendicular magnetic fields, we show that the electron transport reaches the quantum Hall regime with vanishing resistance. Furthermore, quantum Hall transport spectroscopy reveals energy splittings of relativistic Landau levels specific to coupled Dirac surface states. This study provides new insights in the quantum Hall effect of topological insulator (TI) slabs, in the cross-over regime between two-and three-dimensional TIs, and in the relevance of thin TI films to explore novel circuit functionalities in spintronics and quantum nanoelectronics. PACS numbers:Similar to the case of graphene, the charge carriers at the surface of topological insulators are expected to be massless Dirac fermions but with a real spin locked to the momentum [1][2][3]. This has strong implications when the electrons experience a large perpendicular magnetic field B and enter the quantum Hall regime. Indeed, each surface is then characterized by non-degenerate Landau levels (LL) and the associated Hall conductance is expressed as σ xy = (N + h , where N is the LL index. In topological insulator slabs, however, two surface states of extension w have to be considered and are separated by a thickness t. When the wave functions of the two surfaces do not overlap (t w), they are only connected at the boundaries of the sample [4] and the transport properties are obtained by summing the distinct contributions of each surface. The Hall conductance σ xy = (N top + N bottom + 1)h is then expected where N top and N bottom are the LL index for the top and bottom surfaces, respectively. In this regime, integer filling factors ν have been observed in relatively thick strained HgTe [5][6][7] and Bi-based [8, 9] topological insulators. By decreasing t down to w, the two surface states start to overlap giving rise to a non-negligible hybridization energy ∆ [10-12] and the transport then occurs through states delocalized between the two surfaces. Degenerate Dirac LLs are then expected to emerge at high B with energies scaling as √ N B. Moreover, additional dispersive couplings between the two surfaces are expected to lift the LL degeneracy with an energy splitting linear in B [12,13]. While of orbital nature, this splitting reveals the microscopic coupling of spin and orbital degrees of freedom in the Dirac Landau levels. Therefore analysing the energy gaps of both odd and even filling factors and their B-dependences provides a powerful tool to reveal the Dirac surface states of a thin topological insulator slab. Decreasing further t would result in the opening of a large gap in the surface states and the emergence of the quantum spin Hall phase [11][12][13][14].In this letter, the magneto-transport properties of strained HgTe thin films at high magnetic fields are investigated. We study films with a thickness of about 15 nm, characterized by two tunnel-coupled surfaces, where electron transport is solely mediated by surfac...

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“…Molecular beam epitaxy of HgTe/CdTe layers is achieved in a Riber 32 chamber [9]. HgTe layers are grown on either (1 0 0) CdTe or (2 1 1)B CdTe substrates.…”

Section: Mbe Growth Of Hgte/cdte Structuresmentioning

confidence: 99%

“…The aim is to compensate the substrate remaining surface defects and so to perform the growth on a more flat surface. The substrate is then cooled down to the growth temperature for strained HgTe layer [9].…”

Section: Mbe Growth Of Hgte/cdte Structuresmentioning

confidence: 99%

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MBE growth and interfaces characterizations of strained HgTe/CdTe topological insulators

Thomas

Baudry

Barnes

et al. 2015

Journal of Crystal Growth

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MBE Growth of Strained HgTe/CdTe Topological Insulator Structures

Abstract: International audienc

Cited by 20 publications

References 17 publications

Cyclotron-resonance-assisted photocurrents in surface states of a three-dimensional topological insulator based on a strained high-mobility HgTe film

Cyclotron-resonance-assisted photocurrents in surface states of a three-dimensional topological insulator based on a strained high-mobility HgTe film

Revealing topological Dirac fermions at the surface of strained HgTe thin films via quantum Hall transport spectroscopy

MBE growth and interfaces characterizations of strained HgTe/CdTe topological insulators

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