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<p>This study explores the impact of size effects and material composition on the electronic and optical properties of rectangular and cylindrical GaAs/Al<sub>x</sub>Ga<sub>1−x</sub>As core-shell quantum wires. Using the effective mass approximation and assuming a direct bandgap, we analyze confinement energies and emission behavior across cross-sectional areas from 25 to 225 nm<sup>2</sup>. Two alloy compositions are considered: GaAs/Al<sub>0.2</sub>Ga<sub>0.8</sub>As and&#xa0;GaAs/Al<sub>0.4</sub>Ga<sub>0.6</sub>As. The results highlight the combined effects of geometry and aluminum content on electron energy levels and emitted photon wavelengths, providing insights for the design of nanoscale optoelectronic devices. Results for the confinement energy for the first three energy levels, <i>E</i><sub><i>1</i></sub><i>, E</i><sub><i>2</i>,</sub> and <i>E</i><sub><i>3,</i></sub> for GaAs/Al<sub>0.2</sub>Ga<sub>0.8</sub>As and GaAs/Al<sub>0.4</sub>Ga<sub>0.6</sub>As decrease with increasing wire cross-sectional area. All the energy values of the rectangular wires are higher than those of the cylindrical wires for <i>E</i><sub><i>1</i></sub> and <i>E</i><sub><i>2</i></sub>. However, for the third energy level, the energy of the cylindrical wires becomes higher. Related to the wire composition, all the confinement energy of GaAs/Al<sub>0.4</sub>Ga<sub>0.6</sub>As is generally higher than that of GaAs/Al<sub>0.2</sub>Ga<sub>0.8</sub>As, which is due to an increase in the potential barrier height, deepening the quantum well, and increasing energy levels. Conversely, for cross-section areas of 144 to 225 nm<sup>2</sup>, the levels in GaAs/Al<sub>0.4</sub>Ga<sub>0.6</sub>As are lower than those in GaAs/Al<sub>0.2</sub>Ga<sub>0.8</sub>As for all energy levels. Tunneling phenomena are analyzed via transmission coefficient calculations, and the results reveal a great dependency of the transmission coefficient on both cross-sectional areas and material composition. Each energy level has its distinct transmission coefficient value. Finally, the emission radiation from the ground state energy level displays a red wavelength for rectangular and cylindrical wires for all dimensions for GaAs/Al<sub>0.2</sub>Ga<sub>0.8</sub>As,&#xa0;wavelength ranges from 695.2–730.2 nm, for cylindrical wire, and from 683.1–730.8 nm for rectangular wire. While in GaAs/Al<sub>0.6</sub>Ga<sub>0.4</sub>As there is a shift from orange to red light with increasing wire dimensions. Wavelength ranges from 592.5–628.5 nm for cylindrical wire and 590–628.8 nm, for rectangular wire. Notably, wire geometry exerts a minimal influence on ground-state emission performance compared to wire composition. Overall, the findings demonstrate a direct relationship between material composition, structural configuration, and quantum confinement effects. These insights provide valuable guidance for the design and optimization of quantum wire-based optoelectronic devices in nanoscale photonics and electronics.</p>

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Size effects on tunneling and emitted radiation in GaAs/AlxGa1−xAs core-shell rectangular and cylindrical quantum wires

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月2日

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  • M. K. Abu-Assy,
  • Z. A. El-Wahab,
  • Fatin Fadhel Mahmood

摘要

This study explores the impact of size effects and material composition on the electronic and optical properties of rectangular and cylindrical GaAs/AlxGa1−xAs core-shell quantum wires. Using the effective mass approximation and assuming a direct bandgap, we analyze confinement energies and emission behavior across cross-sectional areas from 25 to 225 nm2. Two alloy compositions are considered: GaAs/Al0.2Ga0.8As and GaAs/Al0.4Ga0.6As. The results highlight the combined effects of geometry and aluminum content on electron energy levels and emitted photon wavelengths, providing insights for the design of nanoscale optoelectronic devices. Results for the confinement energy for the first three energy levels, E1, E2, and E3, for GaAs/Al0.2Ga0.8As and GaAs/Al0.4Ga0.6As decrease with increasing wire cross-sectional area. All the energy values of the rectangular wires are higher than those of the cylindrical wires for E1 and E2. However, for the third energy level, the energy of the cylindrical wires becomes higher. Related to the wire composition, all the confinement energy of GaAs/Al0.4Ga0.6As is generally higher than that of GaAs/Al0.2Ga0.8As, which is due to an increase in the potential barrier height, deepening the quantum well, and increasing energy levels. Conversely, for cross-section areas of 144 to 225 nm2, the levels in GaAs/Al0.4Ga0.6As are lower than those in GaAs/Al0.2Ga0.8As for all energy levels. Tunneling phenomena are analyzed via transmission coefficient calculations, and the results reveal a great dependency of the transmission coefficient on both cross-sectional areas and material composition. Each energy level has its distinct transmission coefficient value. Finally, the emission radiation from the ground state energy level displays a red wavelength for rectangular and cylindrical wires for all dimensions for GaAs/Al0.2Ga0.8As, wavelength ranges from 695.2–730.2 nm, for cylindrical wire, and from 683.1–730.8 nm for rectangular wire. While in GaAs/Al0.6Ga0.4As there is a shift from orange to red light with increasing wire dimensions. Wavelength ranges from 592.5–628.5 nm for cylindrical wire and 590–628.8 nm, for rectangular wire. Notably, wire geometry exerts a minimal influence on ground-state emission performance compared to wire composition. Overall, the findings demonstrate a direct relationship between material composition, structural configuration, and quantum confinement effects. These insights provide valuable guidance for the design and optimization of quantum wire-based optoelectronic devices in nanoscale photonics and electronics.