Towards a Germanium and Silicon Laser: The History and the Present

Pelant, I.; Kůsová, Kateřina

doi:10.3390/cryst9120624

Cited by 7 publications

(4 citation statements)

References 35 publications

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“…We first investigate the nonradiative indirect bandgap electron–hole recombination in Si. Si is the cornerstone of the solar photovoltaic industry, , with its prolonged charge carrier lifetime often pinpointed as a crucial determinant of its high energy conversion efficiency. − This can be largely attributed to its indirect bandgap nature . Unfortunately, the underlying physics mechanism is not well understood yet and requires non-Condon effect NA-MD simulations.…”

Section: Resultsmentioning

confidence: 99%

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Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Lu,

Long

2023

J. Am. Chem. Soc.

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Nonradiative multiphonon transitions play a crucial role in understanding charge carrier dynamics. To capture the non-Condon effect in nonadiabatic molecular dynamics (NA-MD), we develop a simple and accurate method to calculate noncrossing and crossing k-point NA coupling in momentum space on an equal footing and implement it with a trajectory surface hopping algorithm. Multiple k-point MD trajectories can provide sufficient nonzero momentum multiphonons coupled to electrons, and the momentum conservation is maintained during nonvertical electron transition. The simulations of indirect bandgap transition in silicon and intra-and intervalley transitions in graphene show that incorporation of the non-Condon effect is needed to correctly depict these types of charge dynamics. In particular, a hidden process is responsible for the delayed nonradiative electron−hole recombination in silicon: the thermal-assisted rapid trapping of an excited electron at the conduction band minimum by a long-lived higher energy state through a nonvertical transition extends charge carrier lifetime, approaching 1 ns, which is about 1.5 times slower than the direct bandgap recombination. For graphene, intervalley scattering takes place within about 225 fs, which can occur only when the intravalley relaxation proceeds to about 50 fs to gain enough phonon momentum. The intra-and intervalley scattering constitute energy relaxation, which completes within sub-500 fs. All the simulated time scales are in excellent agreement with experiments. The study establishes the underlying mechanisms for a long-lived charge carrier in silicon and valley scattering in graphene and underscores the robustness of the non-Condon approximation NA-MD method, which is suitable for rigid, soft, and large defective systems.

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Section: Resultsmentioning

confidence: 99%

“…52−55 This can be largely attributed to its indirect bandgap nature. 56 Unfortunately, the underlying physics mechanism is not well understood yet and requires non-Condon effect NA-MD simulations.…”

Section: Methodsmentioning

confidence: 99%

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Lu,

Long

2023

J. Am. Chem. Soc.

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“…However, the most important inconvenience of this system is the low light absorption-emission efficiency of bulk Si-Ge with an indirect band gap that counts against the long-held goal of integrated group IV photonics. This inconvenience can be solved by nanostructuring (quantum confinement) combined with strain [11][12][13] or by exploiting other crystalline structures different from Fd-3m diamond [14,15], such as metastable hexagonal phase [16]. Other solutions are to develop plasmonic structures [17], to fabricate structures with GeSi quantum dots (QDs) embedded in microresonators [18], or by employing hydrogenation technique for passivating detrimental defects [19], all these enabling the enhancement of GeSi and Ge QDs photoluminescence.…”

Section: Introductionmentioning

confidence: 99%

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

et al. 2021

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Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs–HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.

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“…From a practical perspective, Si–based, efficient, and reliable light-emitting sources have long been considered as the “holy grail” of Si photonics due to the many challenges [ 13 ]. Unfortunately, Group-IV semiconductors, such as Si [ 14 ], Ge [ 15 , 16 ], and GeSi [ 17 , 18 ], which are widely used in integrated circuits, are inefficient light-emitting materials due to their indirect bandgap. Recently, GeSn materials have demonstrated a direct bandgap property, but lasing efficiency at room temperature has still not been demonstrated [ 19 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

Reduced Dislocation of GaAs Layer Grown on Ge-Buffered Si (001) Substrate Using Dislocation Filter Layers for an O-Band InAs/GaAs Quantum Dot Narrow-Ridge Laser

Wei

et al. 2022

Micromachines

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The development of the low dislocation density of the Si-based GaAs buffer is considered the key technical route for realizing InAs/GaAs quantum dot lasers for photonic integrated circuits. To prepare the high-quality GaAs layer on the Si substrate, we employed an engineered Ge-buffer on Si, used thermal cycle annealing, and introduced filtering layers, e.g., strained-layer superlattices, to control/reduce the threading dislocation density in the active part of the laser. In this way, a low defect density of 2.9 × 107 cm−2 could be achieved in the GaAs layer with a surface roughness of 1.01 nm. Transmission electron microscopy has been applied to study the effect of cycling, annealing, and filtering layers for blocking or bending threading-dislocation into the InAs QDs active region of the laser. In addition, the dependence of optical properties of InAs QDs on the growth temperature was also investigated. The results show that a density of 3.4 × 1010 InAs quantum dots could be grown at 450 °C, and the photoluminescence exhibits emission wavelengths of 1274 nm with a fullwidth at half-maximum (FWHM) equal to 32 nm at room temperature. The laser structure demonstrates a peak at 1.27 μm with an FWHM equal to 2.6 nm under a continuous-wave operation with a threshold current density of ∼158 A/cm2 for a 4-μm narrow-ridge width InAs QD device. This work, therefore, paves the path for a monolithic solution for photonic integrated circuits when III−V light sources (which is required for Si photonics) are grown on a Ge-platform (engineered Ge-buffer on Si) for the integration of the CMOS part with other photonic devices on the same chip in near future.

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Towards a Germanium and Silicon Laser: The History and the Present

Cited by 7 publications

References 35 publications

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

Reduced Dislocation of GaAs Layer Grown on Ge-Buffered Si (001) Substrate Using Dislocation Filter Layers for an O-Band InAs/GaAs Quantum Dot Narrow-Ridge Laser

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