Superlattice and Negative Differential Conductivity in Semiconductors

Esaki, L.; Tsu, Raphael

doi:10.1147/rd.141.0061

Cited by 3,242 publications

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“…29,31,32 The second conclusion is especially relevant for optoelectronics, as it implies that hBN-spaced BP stacks have the same light-absorption properties as monolayer BP, with the essential difference that more photons are absorbed due to the increased thickness. Finally, since the operation of BP/hBN/BP as a TFET is based on quantum tunneling, instead of thermionic excitation of carriers, we encounter negative differential resistance (NDR) peaks 33 with peak-to-valley ratios (PVRs) comparable to those predicted for TMDC TFETs, 34 as well as subthreshold swings below the minimum theoretical limit for conventional field effect transistors. 35 We note that intricate heterostructure 2D stacks have already been experimentally obtained, 36 meaning that our proposition of hBN-encapsulated or hBN-spaced BP is realistic.…”

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confidence: 89%

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Multipurpose Black-Phosphorus/hBN Heterostructures

2016

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Black phosphorus (BP) has recently emerged as a promising semiconducting twodimensional material. However, its viability is threatened by its instability in ambient conditions, and by the significant decrease of its band gap in multilayers. We show that one could solve all the aforementioned problems by interfacing BP with hexagonal boron nitride (hBN). To this end, we simulate large, rotated hBN/BP interfaces using linear-scaling density functional theory (DFT). We predict that hBN-encapsulation preserves the main electronic properties of the BP monolayer, while hBN spacers can be used to counteract the band gap reduction in stacked BP. Finally, we propose a model for a tunneling field effect transistor (TFET) based on hBN-spaced BP bilayers.Such BP TFETs would sustain both low-power and fast-switching operations, including negative differential resistance behaviour with peak-to-valley ratios of the same order of magnitude as those encountered in transition metal dichalcogenide TFETs.1 Keywords 2D heterostructures; tunneling transistor; linear-scaling DFT; electric fields Since its inception, the two-dimensional (2D) material community has switched focus several times between different materials, aiming to satisfy different technological requirements. For instance, the lack of a band gap in graphene caused an increased interest in semiconducting transition metal dichalcogenides (TMDCs). While their many qualities have enabled their remarkable success in semiconductor electronics, 1,2 spintronics, 3 and optoelectronics, 2,4 the associated flaws of TMDCs are also of concern. Most notably, they only exhibit a direct band gap when in monolayer form, 5 the carrier mobilities are far smaller than those encountered in graphene, and their large band gap implies that the infrared (IR) spectrum cannot be harnessed by TMDC optoelectronics.In this context, the spotlight has recently shifted to layered black phosphorus (BP), 6,7 a material which rectifies the most important shortcomings of TMDCs. The band gap of BP is direct even in stacked forms, and its value changes significantly with the number of layers: from 0.3 eV in bulk to 1.5-2.0 eV for the monolayer. 8,9 This range of values allows BP to

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confidence: 89%

“…33 Such NDR peaks have applications in oscillatory circuits, memory devices, and even multi-valued logic. 60 This mode is accessible by changing the bias voltage in the previously discussed regime (Fig.…”

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confidence: 99%

Multipurpose Black-Phosphorus/hBN Heterostructures

2016

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“…In 1970 Esaki and Tsu realized the possibility to engineer energy bands by artificially modulating the potential in one direction [27]. They came up with the idea of using a semiconductor superlattice and predicted the onset of negative differential conductivity.…”

Section: Confining Electronsmentioning

confidence: 99%

Artificial honeycomb lattices for electrons, atoms and photons

et al. 2013

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Artificial honeycomb lattices offer a tunable platform to study massless Dirac quasiparticles and their topological and correlated phases. Here we review recent progress in the design and fabrication of such synthetic structures focusing on nanopatterning of two-dimensional electron gases in semiconductors, molecule-by-molecule assembly by scanning probe methods, and optical trapping of ultracold atoms in crystals of light. We also discuss photonic crystals with Dirac cone dispersion and topologically protected edge states. We emphasize how the interplay between single-particle band structure engineering and cooperative effects leads to spectacular manifestations in tunneling and optical spectroscopies.

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“…The seminal work of Esaki and Tsu [4] drew attention to the fact that the relatively large scale periodic structures in semiconductor superlattices made them ideal solids in which to explore and use Bloch oscillation. Following this work that predicted that electrically biased semiconductor superlattices will exhibit negative differential conductivity (NDC) [4] like the Gunn effect, Ktitorov et al showed theoretically that the negative resistance and potential gain should persists up the Bloch frequency or spacing between the rungs of the Stark ladder [5]. Unlike the Gunn effect which persists only up to the energy relaxation rate, 100-200 GHz, electrically biased semiconductor superlattices should exhibit gain over a much larger band width, up to several terahertz.…”

Section: Introductionmentioning

confidence: 99%

Loss and gain in Bloch oscillating super-superlattices: THz Stark ladder spectroscopy

Robrish

Kobayashi

et al. 2006

Physica E: Low-dimensional Systems and Nanostructures

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Bloch oscillation in electrically biased semiconductor superlattices offer broadband terahertz gain from DC up to the Bloch frequency or Stark splitting. Useful gain up to 2-3 terahertz can provide a basis for solid-state electronic oscillators operating at 10 times the frequency of existing devices.A major stumbling block is the inherent instability of the electrically biased doped superlattices to the formation of static or dynamic electric field domains. To circumvent this, we have fabricated super-superlattices in which a large superlattice is punctuated with heavily doped regions. The short superlattice sections have subcritical "nl" products Room temperature, terahertz photon assisted transport in short InGaAs/InAlAs superlattice cells allows us to determine the Stark ladder splitting as the superlattice is electrically biased and confirms the absence of electric field domains in short structures.Absorption of radiation from 1.5 to 2.5 THz by electrically biased InAs/AlSb super-superlattices exhibit a crossover from loss to gain as the Stark ladder is opened. Measurements are carried out at room temperature in a novel planar terahertz waveguide defined by photonic band gap sidewalls and loaded with an array of electrically biased super-superlattices. The frequency dependent crossover voltage indicates ~ 80% participation of the super-superlattice.

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Superlattice and Negative Differential Conductivity in Semiconductors

Cited by 3,242 publications

References 2 publications

Multipurpose Black-Phosphorus/hBN Heterostructures

Multipurpose Black-Phosphorus/hBN Heterostructures

Artificial honeycomb lattices for electrons, atoms and photons

Loss and gain in Bloch oscillating super-superlattices: THz Stark ladder spectroscopy

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