Electron-Phonon Interaction in Semiconducting Layer Structures

Fivaz, Roland; Mooser, E.

doi:10.1103/physrev.136.a833

Cited by 85 publications

(44 citation statements)

References 4 publications

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“…One of the reasons for the decrease in anisotropy in GaSe:Ge crystals as the temperature is increased may be that the bridges formed between layers by Ge atoms, as in the Mn + , Li + , Na + , and Cd + cases, become more effective at these temperatures [24]. In the deformation potential approximation, in the temperature dependence of exciton states there are several interactions like phonon-phonon anharmonic interactions and exciton-optical/acoustic phonon interactions [25][26][27][28]. To gain knowledge about the rigid layer phonon modes and optical and acoustic phonons, which are characteristic of layered crystals and may be involved in the exciton ionization process [28], we have studied the temperature dependence of the peak energy position and FWHM of exciton photoconductivity and absorption spectra.…”

Section: Originalmentioning

confidence: 99%

Exciton photoconductivity in Ge‐doped GaSe crystals

Mamedov

Karabulut

Kodolbaş

et al. 2005

Physica Status Solidi (b)

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Spectral photoconductivity in Ge-doped GaSe crystals was investigated as a function of temperature. It is found that when the crystal is doped with small concentrations of Ge atoms (0.01 at%), the photoconductivity is carried out by the ionization of the excitons. In these crystals, exciton photoconductivity is found to have an Urbach tail similar to the tail observed in exciton absorption. Investigation of the temperature dependence of the peak positions (E exc (T)) and line widths (Г exc (T)) of the photoconductivity spectra indicates that the exciton ionization is due to the exciton-phonon and exciton-impurity interactions. From the analyses of the E exc (T) and Г exc (T) data, it is found that at low temperatures (T < 50 K) the exciton-phonon interaction takes place via rigid-layer phonon modes while in the 50 -300 K temperature range it takes place via phonons with hν p ≈ 18 meV. In the 300 -450 K range the energy of the phonons involved in the exciton-phonon interaction is hν p ≈ 36 meV. The anisotropy observed in the exciton photoconductivity taken parallel and perpendicular to the layers of doped GaSe crystals diminishes at T = 300 K and the peak positions of the photoconductivity in both directions coincide with the peak position of the free exciton peak (n = 1) in the absorption spectrum. Another important result found is that in these layered GaSe crystals the exciton states continue to exist at high temperatures, up to 450 K.

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Section: Originalmentioning

confidence: 99%

Exciton photoconductivity in Ge‐doped GaSe crystals

Mamedov

Karabulut

Kodolbaş

et al. 2005

Physica Status Solidi (b)

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“…We have confirmed that both MoS 2 and WS 2 monolayers are very stable and this mild annealing process cannot cause any change in the quality and crystalline structures of the materials. heterostructures on the epitaxy and orientation of the stacking suggests a strong electron-phonon coupling in 2D materials 39 . The electron-photon coupling could be so strong that able to efficiently compensate whatever momentum mismatch for the charge transfer between the monolayers.…”

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confidence: 99%

Equally Efficient Interlayer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS₂/WS₂ Heterostructures

Yu¹,

Shou-song²,

et al. 2014

Nano Lett.

354

386

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Ridge National Laboratory, Oak Ridge, Tennessee 37831 § These authors contribute equally. AbstractSemiconductor heterostructures provide a powerful platform to engineer the dynamics of excitons for fundamental and applied interests. However, the functionality of conventional semiconductor heterostructures is often limited by inefficient charge transfer across interfaces due to the interfacial imperfection caused by lattice mismatch. Here we demonstrate that MoS 2 /WS 2 heterostructures consisting of monolayer MoS 2 and WS 2 stacked in the vertical direction can enable equally efficient interlayer exciton relaxation regardless the epitaxy and orientation of the stacking. This is manifested by a similar two orders of magnitude decrease of

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“…Consequently, the charge carriers can be treated approximately as if they are transporting through a stack of independent layers of a 2D structure. [22][23][24][25][26] On the other hand, compared to other layered semiconductors such as GaSe, MoS 2 , MoSe 2 , and WSe 2 , [23][24][25] which typically have an energy bandgap E g ∼ 2 eV with a maximum optical phonon energy -hω ∼ 60 meV, hBN is composed of light elements B and N and has a much larger bandgap (E g ∼ 6.4 eV) 5 as well as a much larger maximum longitudinal optical (LO) phonon energy of -hω ∼ 190 meV. 22,27 In fact, hBN may possess the largest phonon energy among all semiconductors.…”

Section: Resultsmentioning

confidence: 99%

“…It has been reported that the scattering is dominated by homopolar optical phonons in layer structured semiconductors with energy gaps around 2 eV, [23][24][25][26] in which the temperature dependence follows µ ∼ T −α with much large exponents than in 3D and isotropic semiconductors. For instance, α ≈ 2.1 for GaSe and α ≈ 2.6 for MoS 2 have been measured.…”

Section: Resultsmentioning

confidence: 99%

“…21 The layer structured hBN on the other hand has the same crystal structure as graphite with lattice constants a = 2.54 Å and c = 6.66 Å. Consequently, like graphite its physical properties are expected to be anisotropic. [22][23][24][25][26] For instance, although hBN bulk crystals and epilayers are three-dimensional (3D) systems, the interlayer optical transitions are much weaker than those within the layers 4 and the exciton properties of 3D hBN can be described in a 2D framework. 5 Due to the highly anisotropic nature of hBN, it is also expected that phonons propagate more quickly in the c-plane (⊥ c-axis) with strong B-N bonds and slower along the c-axis (// c-axis) with Van der Waals bonds.…”

Section: Resultsmentioning

confidence: 99%

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Charge carrier transport properties in layer structured hexagonal boron nitride

Doan

Lin

et al. 2014

AIP Advances

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Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)−α with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

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Electron-Phonon Interaction in Semiconducting Layer Structures

Cited by 85 publications

References 4 publications

Exciton photoconductivity in Ge‐doped GaSe crystals

Exciton photoconductivity in Ge‐doped GaSe crystals

Equally Efficient Interlayer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS₂/WS₂ Heterostructures

Charge carrier transport properties in layer structured hexagonal boron nitride

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Electron-Phonon Interaction in Semiconducting Layer Structures

Cited by 85 publications

References 4 publications

Exciton photoconductivity in Ge‐doped GaSe crystals

Exciton photoconductivity in Ge‐doped GaSe crystals

Equally Efficient Interlayer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS2/WS2 Heterostructures

Charge carrier transport properties in layer structured hexagonal boron nitride

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Product

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Equally Efficient Interlayer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS₂/WS₂ Heterostructures