Optical properties of stacked Ge/Si quantum dots with different spacer thickness grown by chemical vapor deposition

Chen, Wen Yen; Chang, Wen‐Hao; Chou, A. T.; Hsu, T. M.; Chen, Pan Shiu; Pei, Zingway; Lai, Li-Shyue

doi:10.1016/j.apsusc.2003.08.040

Cited by 10 publications

(6 citation statements)

References 9 publications

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“…28,29 Such laser excitation scenarios were also found to be similarly successful in pairs of QDs. 14,30,31 Another strategy for electron and hole separation in pairs of QDs, or double quantum dots (DQDs), is potential-driven charge-carrier tunneling following photoexcitation. 32,33 In this work, we explore exciton stabilization by hole trapping in combination with electron migration in selfassembled germanium DQDs.…”

Section: ■ Introductionmentioning

confidence: 99%

“…A promising material class in this respect is germanium QDs on a silicon surface . Their optical structure is already well-investigated experimentally, and particular states can be addressed by lasers. , Such laser excitation scenarios were also found to be similarly successful in pairs of QDs. ,, Another strategy for electron and hole separation in pairs of QDs, or double quantum dots (DQDs), is potential-driven charge-carrier tunneling following photoexcitation. , …”

Section: Introductionmentioning

confidence: 99%

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Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

2021

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The creation, transfer, and stabilization of localized excitations are studied in a donor–acceptor Frenkel exciton model in an atomistic treatment of reduced-size double quantum dots (QDs) of various sizes. The explicit time-dependent dynamics simulations carried out by hybrid time-dependent density functional theory/configuration interaction show that laser-controlled hole trapping in stacked, coupled germanium/silicon quantum dots can be achieved by a UV/IR pump–dump pulse sequence. The first UV excitation creates an exciton localized on the topmost QD and after some coherent transfer time, an IR pulse dumps and localizes an exciton in the bottom QD. While hole trapping is observed in each excitation step, we show that the stability of the localized electron depends on its multiexcitonic character. We present how size and geometry variations of three Ge/Si nanocrystals influence transfer times and thus the efficiency of laser-driven populations of the electron–hole pair states.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

2021

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“…Significant research has been carried out into obtaining direct band gap emission from group-IV semiconductor alloys, strained epitaxial films using a silicon nitride stressor layer, and defect engineered nanostructures for the realization of Sicompatible optical sources [1][2][3][4][5][6][7][8][9][10][11][12]. Recently, Sn doped Ge nanostructures have attracted much interest due to their possible integration with Si technology as a direct band gap material, which holds immense promise for group IV-based efficient light-emitting devices.…”

Section: Introductionmentioning

confidence: 99%

Emission characteristics of self-assembled strained Ge_1−xSn_xislands for sources in the optical communication region

et al. 2017

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Self-assembled strained Ge Sn islands on Si (100) have been grown at a low temperature using molecular beam epitaxy. The in-built strain and fraction of Sn in the islands have been estimated using x-ray photoelectron spectroscopy and high resolution x-ray diffraction study of grown samples. No-phonon assisted transition in the optical communication wavelength range of 1.4-1.8 μm has been observed in the Ge Sn island samples. The direct band gap transition intensity is found to increase with a growth in Sn concentration, with this increase in intensity sustained up to a temperature of 130 K in Ge Sn islands. The observed electroluminescence in p-i-n devices fabricated on Ge Sn island samples above a threshold bias of 4 V makes them attractive for future Si based optical devices.

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“…These type-II semiconductor heterostructures stand out by their large valence-band offset (∼0.7 eV), which engenders an electron hole localization in the Ge regions and an electron confinement in the Si layers. , Despite the difficulties due to the lattice mismatch between Si and Ge, multiple fabrication methods − have been developed to enable the control of the composition, size, and growth of these Ge/Si systems. Meanwhile, considerable progress has been achieved in the detection and analysis of the spatial quantum confinement of charge carriers and optical transitions in Ge/Si heterostructures − for potential applications such as light-emitting diodes, , solar cells, , or quantum computers …”

Section: Introductionmentioning

confidence: 99%

Laser-Driven Hole Trapping in a Ge/Si Core–Shell Nanocrystal: An Atomistic Configuration Interaction Perspective

Hermann

Tremblay

2015

J. Phys. Chem. C

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This contribution reports on the first example of laser-driven charge carrier confinement in a solid state quantum dot investigated using a fully atomistic, correlated many-electron ansatz. Specifically, a Ge/Si model nanocrystal is designed to retain the main structural characteristics and excitonic properties of experimentally observed self-assembled pyramidal heterostructures. State-selective laser excitations yielding hole confinement in the Ge nanostructure are simulated using the reduced density matrix variant of the time-dependent configuration interaction method (ρ-TDCI). The degree of carrier localization in the quantum dot is determined by analyzing the correlated one-electron densities from configuration interaction electronic states at a singles level. Additionally, dissipation and pure dephasing are included to treat the coupling of the local core−shell structure with the vibrations of the surrounding silicon matrix. For this purpose, a new microscopic model for these nonadiabatic coupling rates is derived. The results reveal that, despite the presence of dissipation, charge carriers can be efficiently confined by localized optical excitations in the model Ge/Si quantum dot to create long-lived, large permanent dipoles in the nanocrystal.

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Optical properties of stacked Ge/Si quantum dots with different spacer thickness grown by chemical vapor deposition

Cited by 10 publications

References 9 publications

Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

Emission characteristics of self-assembled strained Ge_1−xSn_xislands for sources in the optical communication region

Laser-Driven Hole Trapping in a Ge/Si Core–Shell Nanocrystal: An Atomistic Configuration Interaction Perspective

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Optical properties of stacked Ge/Si quantum dots with different spacer thickness grown by chemical vapor deposition

Cited by 10 publications

References 9 publications

Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

Atomistic Simulations of Laser-Controlled Exciton Transfer and Stabilization in Symmetric Double Quantum Dots

Emission characteristics of self-assembled strained Ge1−xSnxislands for sources in the optical communication region

Laser-Driven Hole Trapping in a Ge/Si Core–Shell Nanocrystal: An Atomistic Configuration Interaction Perspective

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Emission characteristics of self-assembled strained Ge_1−xSn_xislands for sources in the optical communication region