Near-Infrared Photoresponse in Ge/Si Quantum Dots Enhanced by Photon-Trapping Hole Arrays

Group-IV photonic devices that contain Si and Ge are very attractive due to their compatibility with integrated silicon photonics platforms. Despite the recent progress in fabrication of Ge/Si quantum dot (QD) photodetectors, their low quantum efficiency still remains a major challenge and different approaches to improve the QD photoresponse are under investigation. In this paper, we report on the fabrication and optical characterization of Ge/Si QD pin photodiodes integrated with photon-trapping microstructures for near-infrared photodetection. The photon traps represent vertical holes having 2D periodicity with a feature size of about 1 μm on the diode surface, which significantly increase the normal incidence light absorption of Ge/Si QDs due to generation of lateral optical modes in the wide telecommunication wavelength range. For a hole array periodicity of 1700 nm and hole diameter of 1130 nm, the responsivity of the photon-trapping device is found to be enhanced by about 25 times at λ=1.2 μm and by 34 times at λ≈1.6 μm relative to a bare detector without holes. These results make the micro/nanohole Ge/Si QD photodiodes promising to cover the operation wavelength range from the telecom O-band (1260–1360 nm) up to the L-band (1565–1625 nm).

Exploring the behaviors of electrode-driven Si quantum dot systems: from charge control to qubit operations

Quantum logic operations and electron spin controls in a Si double quantum dot platform is studied with a multi-scale modeling approach that can open the pathway to explore engineering details for Si-based designs of robust quantum logic gates.

Cellular Uptake and Magneto-Hyperthermia Induced Cytotoxicity using Photoluminescent Fe3O4 Nanoparticle/Si Quantum Dot Hybrids

<p>The design and fabrication of Si-based multi-functional nanomaterials for biological and biomedical applications is an active area of research. The potential benefits of using Si-based nanomaterials are not only due to their size/surface-dependent optical responses but also the high biocompatibility and low-toxicity of silicon itself. Combining these characteristics with the magnetic properties of Fe₃O₄ nanoparticles (NPs) multiplies the options available for real-world applications. In the current study, biocompatible magnetofluorescent nano-hybrids have been prepared by covalent linking of Si quantum dots to water-dispersible Fe₃O₄ NPs <i>via</i> dicyclohexylcarbodiimide (DCC) coupling. We explore some of the properties of these magnetofluorescent nano-hybrids as well as evaluate uptake, the potential for cellular toxicity, and the induction of acute cellular oxidative stress in a mast cells-like cell line (RBL-2H3) by heat induction through short-term radio frequency modulation (10 min @ 156 kHz, 500 A). We found that the NPs were internalized readily by the cells and also penetrated the nuclear membrane. Radio frequency activated nano-hybrids also had significantly increased cell death where > 50% of the RBL-2H3 cells were found to be in an apoptotic or necrotic state, and that this was attributable to increased triggering of oxidative cell stress mechanisms. </p>

Cellular Uptake and Magneto-Hyperthermia Induced Cytotoxicity using Photoluminescent Fe3O4 Nanoparticle/Si Quantum Dot Hybrids

<p>The design and fabrication of Si-based multi-functional nanomaterials for biological and biomedical applications is an active area of research. The potential benefits of using Si-based nanomaterials are not only due to their size/surface-dependent optical responses but also the high biocompatibility and low-toxicity of silicon itself. Combining these characteristics with the magnetic properties of Fe₃O₄ nanoparticles (NPs) multiplies the options available for real-world applications. In the current study, biocompatible magnetofluorescent nano-hybrids have been prepared by covalent linking of Si quantum dots to water-dispersible Fe₃O₄ NPs <i>via</i> dicyclohexylcarbodiimide (DCC) coupling. We explore some of the properties of these magnetofluorescent nano-hybrids as well as evaluate uptake, the potential for cellular toxicity, and the induction of acute cellular oxidative stress in a mast cells-like cell line (RBL-2H3) by heat induction through short-term radio frequency modulation (10 min @ 156 kHz, 500 A). We found that the NPs were internalized readily by the cells and also penetrated the nuclear membrane. Radio frequency activated nano-hybrids also had significantly increased cell death where > 50% of the RBL-2H3 cells were found to be in an apoptotic or necrotic state, and that this was attributable to increased triggering of oxidative cell stress mechanisms. </p>

Long-wave Absorption of Few-Hole Gas in Prolate Ellipsoidal Ge/Si Quantum Dot: Implementation of Analytically Solvable Moshinsky Model

In this paper, the behavior of a heavy hole gas in a strongly prolate ellipsoidal Ge/Si quantum dot has been investigated. Due to the specific geometry of the quantum dot, the interaction between holes is considered one-dimensional. Based on the adiabatic approximation, it is shown that in the z-direction, hole gas is localized in a one-dimensional parabolic well. By modeling the potential of pair interaction between holes in the framework of oscillatory law, the problem is reduced to a one-dimensional, analytically solvable Moshinsky model. The exact energy spectrum of the few-hole gas has been calculated. A detailed analysis of the energy spectrum is presented. The character of long-wave transitions between the center-of-mass levels of the system has been obtained when Kohn theorem is realized.

PHYSICS PHENOMENA IN SILICON BASED QUANTUM DOT STRUCTURES FOR NANOELECTRONICS, NANOPHOTONIC AND SPINTRONIC

The report is review of physical phenomena in Ge/Si quantum dot nano heterostructures