Low Temperature Processing of Nanostructures Based on II-VI Semiconductors Quantum Wells

Majewicz, Magdalena; Śnieżek, D.; Wojciechowski, Tomasz; Baran, Emily B.; Nowicki, P.; Wójtowicz, T.; Wróbel, J.

doi:10.12693/aphyspola.126.1174

Cited by 5 publications

(2 citation statements)

References 12 publications

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“…In addition, samples S2 and S3 had a top gate electrode allowing for carrier density control. 42 Figure 2a, b shows the layer sequence scheme and highresolution electron microscopy (HREM) images of the cross section of sample S1. A perfect alignment of the successive atomic layers with the well-defined HgTe QW can be seen in Fig.…”

Section: Investigated Structuresmentioning

confidence: 99%

Magneto-transport in inverted HgTe quantum wells

Yahniuk¹,

Криштопенко²,

Grabecki³

et al. 2019

npj Quantum Mater.

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HgTe quantum wells (QWs) are two-dimensional semiconductor systems that change their properties at the critical thickness d c , corresponding to the band inversion and topological phase transition. The motivation of this work was to study magnetotransport properties of HgTe QWs with thickness approaching d c , and examine them as potential candidates for quantum Hall effect (QHE) resistance standards. We show that in the case of d > d c (inverted QWs), the quantization is influenced by coexistence of topological helical edge states and QHE chiral states. However, at d ≈ d c , where QW states exhibit a graphene-like band structure, an accurate Hall resistance quantization in low magnetic fields (B ≤ 1.4 T) and at relatively high temperatures (T ≥ 1.3 K) may be achieved. We observe wider and more robust quantized QHE plateaus for holes, which suggests-in accordance with the "charge reservoir" model-a pinning of the Fermi level in the valence band region. Our analysis exhibits advantages and drawbacks of HgTe QWs for quantum metrology applications, as compared to graphene and GaAs counterparts.

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Section: Investigated Structuresmentioning

confidence: 99%

Magneto-transport in inverted HgTe quantum wells

Yahniuk¹,

Криштопенко²,

Grabecki³

et al. 2019

npj Quantum Mater.

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“…Measurements were performed on lithographically defined Hall bars with the dimensions of L × W = 80 × 20 µm 2 , and L × W = 40 × 20 µm 2 (samples S1 and S2, respectively) and L × W = 650 × 50 µm 2 (sample S3 ). Additionally, samples S2 and S3 had a top gate electrode allowing for carrier density control [36].…”

Section: A Investigated Structuresmentioning

confidence: 99%

Perspectives of HgTe Topological Insulators for Quantum Hall Metrology

Yahniuk,

Krishtopenko,

Grabecki

et al. 2018

Preprint

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We report the studies of high-quality HgTe/(Cd,Hg)Te quantum wells (QWs) with a width close to the critical one dc, corresponding to the topological phase transition and graphene like band structure in view of their applications for Quantum Hall Effect (QHE) resistance standards. We show that in the case of inverted band ordering, the coexistence of conducting topological helical edge states together with QHE chiral states degrades the precision of the resistance quantization. By experimental and theoretical studies we demonstrate how one may reach very favorable conditions for the QHE resistance standards: low magnetic fields allowing to use permanent magnets (B ≤ 1.4 T) and simultaneously realtively high teperatures (liquid helium, T ≥ 1.3 K). This way we show that HgTe QW based QHE resistance standards may replace their graphene and GaAs counterparts and pave the way towards large scale fabrication and applications of QHE metrology devices. I. INTRODUCTIONMercury cadmium telluride (Hg 1−x Cd x Te) zinc-blende compounds are an example of rare semiconductor materials that form alloys over the whole composition range x while keeping the same crystal structure and the virtually unaltered lattice parameters. [1, 2] Accordingly, it is possible to tune the band structure by changing x and grow bulk films, two-dimensional (2D) quantum wells (QWs) or superlattices without strain-related material degradation. In this sense, Hg 1−x Cd x Te crystals are similar to the well-known Ga 1−x Al x As semiconductors, but show a much larger energy band-gap tunability, with band gaps ranging from E g ≡ E Γ6 -E Γ8 = 1.6 eV for CdTe to the inverted band ordering, with E g ≈ -0.30 eV for HgTe at 4.2 K. [1] This peculiar aspect of Hg 1−x Cd x Te allows to reach E g ≈ 0 eV [2-4] and the conditions for observation of 3D carriers with massless Dirac-like linear dispersion and with high values of room-and low-temperature electron mobilities reaching 3.5•10 4 and 2•10 6 cm 2 V −1 s −1 , respectively [5]. Moreover, since it is possible to adjust the bandgap below 100 meV, Hg 1−x Cd x Te-based systems are broadly employed in infrared and terahertz detectors [6], cameras [7], and lasers [8].Recent technological advances in molecular beam epitaxy (MBE) of Hg 1−x Cd x Te-based quantum structures

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