Single Photon Emission Achieved in Thin GaAs/GaAsN/GaAs Core-Multishell Nanowires Grown on Silicon

Core Concepts

This research paper reports the successful growth of thin GaAs/GaAsN/GaAs core-multishell nanowires on silicon substrates and, for the first time, the demonstration of single photon emission from these nanowires, paving the way for their use in quantum photonic devices and circuits.

Abstract

• Bibliographic Information: Denis, N., Dede, D., Nurmamytov, T., Cianci, S., Santangeli, F., Felici, M., Boureau, V., Polimeni, A., Rubini, S., Fontcuberta i Morral, A., & De Luca, M. (2024). Single photon emitters in thin GaAsN nanowire tubes grown on Si. arXiv preprint arXiv:2411.03185.
• Research Objective: To grow high-quality, thin GaAs/GaAsN/GaAs core-multishell nanowires on silicon substrates and investigate their potential as single photon emitters for quantum photonic applications.
• Methodology:
  • Growth of GaAs/GaAsN/GaAs core-multishell nanowires on Si (111) substrates using plasma-assisted molecular beam epitaxy (MBE).
  • Structural characterization of nanowires using transmission electron microscopy (TEM) and ultramicrotomy.
  • Optical characterization using micro-photoluminescence (µ-PL) spectroscopy at various temperatures and excitation powers.
  • Single photon emission analysis using Hanbury-Brown and Twiss setup and time-resolved photoluminescence measurements.
• Key Findings:
  • Successful growth of thin, vertically-oriented, and defect-free GaAs/GaAsN/GaAs core-multishell nanowires with a pure zincblende crystal phase.
  • Observation of strong and narrow excitonic emission lines from the GaAsN shell at low temperatures, indicative of quantum dot-like states.
  • Demonstration of single photon emission with a g²(τ) value of 0.056 at zero time delay, confirming the high purity of the emitted single photons.
• Main Conclusions:
  • The thin GaAsN shell, combined with the high crystalline quality of the nanowires, enables the creation of localized exciton states that act as efficient single photon emitters.
  • This work introduces GaAs/GaAsN nanowires as a new platform for single photon sources that can be monolithically integrated on silicon, opening possibilities for on-chip quantum photonic devices.
• Significance:
  • This research significantly advances the field of solid-state single photon sources by demonstrating a new material system and nanostructure design for efficient single photon emission.
  • The monolithic integration on silicon substrates makes these nanowire-based single photon emitters highly promising for scalable and integrated quantum photonic circuits and technologies.
• Limitations and Future Research:
  • Further investigation into the optimization of nanowire growth parameters to achieve even brighter and more efficient single photon emission.
  • Exploration of integrating these nanowire single photon emitters into photonic cavities or waveguides to enhance their performance and enable on-chip manipulation of single photons.

Stats

The GaAsN shell thickness is approximately 10 nm.
The N concentration in the GaAsN shell is approximately 2.7%.
The single photon emission showed a g2(0) value of 0.056.
The decay time of the single photon emitter was measured to be 16.0 ns.

Quotes

"This work introduces GaAs/GaAsN NWs to the panorama of III-V single photon emitters that can be monolithically integrated on Si."
"In conclusion, we have designed a NW system that is suitable to create fiber-coupled plug-and-play devices based on single photon emitters monolithically integrated on Si."

Key Insights Distilled From

Single photon emitters in thin GaAsN nanowire tubes grown on Si

by Nadine Denis... at arxiv.org 11-06-2024

https://arxiv.org/pdf/2411.03185.pdf

Deeper Inquiries

How could the growth process be further refined to control the wavelength of the emitted single photons from these nanowires?

Controlling the wavelength of emitted photons from GaAs/GaAsN/GaAs core-multishell nanowires can be achieved by fine-tuning the nanowire properties during the growth process. Here are some potential approaches:

Nitrogen Concentration: The most direct way to control the emission wavelength is by carefully adjusting the nitrogen concentration in the GaAsN shell. As stated in the article, the incorporation of nitrogen into GaAs significantly reduces the bandgap, leading to a redshift in the emitted photon wavelength. A higher nitrogen concentration results in a lower bandgap and thus a longer emission wavelength. This can be achieved by adjusting the growth parameters, such as the nitrogen plasma power, growth temperature, and the V/III ratio during the GaAsN shell growth.

Shell Thickness: Quantum confinement effects are highly sensitive to the dimensions of the confining structure. By precisely controlling the thickness of the GaAsN shell, one can fine-tune the energy levels within the quantum dots and thus the emission wavelength. Thinner shells lead to stronger confinement and a larger bandgap, resulting in a blueshift of the emitted photons.

Strain Engineering: The article highlights the presence of strain in the core-shell structure due to the lattice mismatch between GaAs and GaAsN. This strain can be intentionally manipulated to further control the bandgap and emission wavelength. By adjusting the relative thicknesses of the core and shell layers, or by introducing additional shell layers with different lattice constants, it is possible to engineer the strain profile within the nanowire and fine-tune the emission wavelength.

Alloy Composition: Exploring the incorporation of other elements, such as indium, into the GaAsN shell (forming GaInAsN) can provide additional degrees of freedom for bandgap engineering. By carefully controlling the alloy composition, it is possible to achieve emission wavelengths spanning a wider range within the near-infrared spectrum.

Axial Growth Control: The article mentions the presence of a short Wurtzite segment at the tip of the nanowires. By controlling the growth conditions, it might be possible to engineer the length or even the presence of this segment. This could be used to create a specific type of quantum dot or to modify the strain profile in the nanowire, ultimately influencing the emission wavelength.

By carefully optimizing these growth parameters, researchers can achieve precise control over the emission wavelength of single photons from these GaAs/GaAsN/GaAs core-multishell nanowires, making them highly valuable for various quantum communication and computing applications.

Could defects or strain in the nanowires be intentionally engineered to create even more localized states and enhance single photon emission?

Yes, intentionally engineering defects or strain in the nanowires presents a promising avenue for creating even more localized states and enhancing single photon emission. Here's how:

Defect Engineering:

Quantum Dot Formation: Introducing controlled defects, such as nitrogen vacancies or clusters, within the GaAsN shell can act as artificial nucleation sites for quantum dots. These defects create localized potential minima within the crystal lattice, effectively trapping excitons and promoting single photon emission.

Emission Wavelength Tuning: The energy levels of these defect-bound excitons are distinct from the intrinsic bandgap of GaAsN, offering an additional parameter for tuning the emission wavelength. By controlling the type and density of defects, it's possible to achieve emission at desired wavelengths.

Strain Engineering:

Strain-Induced Quantum Confinement: As mentioned earlier, strain modifies the bandgap of semiconductors. By intentionally introducing strain gradients or localized strain fields within the nanowire, one can create potential wells that confine excitons, similar to quantum dots. This can be achieved through techniques like patterned growth, where the nanowire diameter is modulated, or by partially embedding the nanowire in a material with a different lattice constant.

Enhanced Exciton Localization: Strain can also enhance the localization of excitons within existing quantum dots. By strategically engineering the strain profile around a quantum dot, it's possible to increase the binding energy of the exciton, making it more robust against thermal ionization and improving the single photon emission purity.

Combined Approach:

Synergistic Effects: Combining defect and strain engineering offers a powerful strategy for tailoring the optical properties of nanowires. For instance, introducing defects within a strained region can lead to the formation of highly localized states with unique emission characteristics.

Challenges and Considerations:

Control and Reproducibility: Precisely controlling the type, location, and density of defects or strain fields within nanoscale structures remains a significant challenge. Achieving high reproducibility is crucial for practical applications.

Non-Radiative Recombination: While defects can enhance exciton localization, they can also introduce non-radiative recombination pathways, reducing the overall efficiency of single photon emission. Careful optimization is needed to balance these competing effects.

By addressing these challenges and harnessing the potential of defect and strain engineering, researchers can pave the way for brighter and more tunable single photon sources based on GaAs/GaAsN/GaAs core-multishell nanowires.

What are the potential long-term implications of developing efficient and scalable single photon sources for quantum communication and computing technologies?

Developing efficient and scalable single photon sources stands as a cornerstone for unlocking the full potential of quantum communication and computing technologies. Here are some long-term implications:
Quantum Communication:

Ultra-Secure Communication: Single photons, being the smallest unit of light, are inherently resistant to eavesdropping. Quantum communication relies on the principles of quantum mechanics to establish secure communication channels, where any attempt to intercept or measure the transmitted information would inevitably disturb the quantum state, alerting the communicating parties.

Quantum Key Distribution (QKD): QKD is a prominent application of quantum communication that enables the secure distribution of encryption keys between distant parties. Efficient single photon sources are crucial for practical QKD systems, enabling faster key generation rates and longer communication distances.

Quantum Networks: Building large-scale quantum networks requires interconnecting multiple quantum devices, such as quantum computers or quantum sensors, over long distances. Single photon sources will serve as essential building blocks for these networks, enabling the transmission of quantum information between nodes.

Quantum Computing:

Linear Optical Quantum Computing: This paradigm of quantum computing relies on single photons as qubits and linear optical elements for processing quantum information. Efficient and scalable single photon sources are essential for realizing complex quantum computations using this approach.

Quantum Measurement and Sensing: Single photon sources play a vital role in various quantum measurement techniques, such as quantum microscopy and quantum sensing. They enable the precise detection and manipulation of individual quantum systems, leading to enhanced sensitivity and resolution.

Other Implications:

Fundamental Research: Developing efficient single photon sources will continue to advance our understanding of fundamental quantum phenomena, such as entanglement and quantum measurement.

New Technologies and Industries: The development of scalable single photon sources is likely to spur innovation in related fields, such as nanophotonics, materials science, and semiconductor manufacturing, leading to new technologies and industries.

Challenges and Outlook:
While the potential benefits are vast, realizing practical quantum technologies based on single photon sources requires overcoming significant challenges, including:

Efficiency and Scalability: Current single photon sources often suffer from low efficiency and are challenging to scale up to large numbers.

Indistinguishability: For many applications, it's crucial to have single photon sources that emit photons with identical properties (indistinguishable photons).

Integration: Integrating single photon sources with other quantum devices and systems remains a significant hurdle.

Despite these challenges, the continuous progress in materials science, nanofabrication, and quantum engineering promises a bright future for efficient and scalable single photon sources, paving the way for transformative advancements in quantum communication, computing, and beyond.