scholarly journals Depopulation mechanism for incoherent terahertz source – THz torch – based on GaAsBi/GaAs quantum well in GaAs/AlGaAs parabolic quantum well

2020 ◽  
Vol 60 (2) ◽  
Author(s):  
Mindaugas Karaliūnas ◽  
Andres Udal ◽  
Gintaras Valušis
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Phonon Scattering ◽  
Transition Probability ◽  
Power Spectra ◽  
Radiative Transition ◽  
Promising Candidate ◽  
New Approach ◽  
Radiative Power ◽  
Parabolic Quantum Wells

Parabolic quantum wells (PQWs) are known as a promising candidate for a compact terahertz (THz) source. PQWs have equidistant subbands that can be designed to be separated by few meV to meet the THz frequency range. To enhance the efficiency and power of THz emission from PQWs, a new approach is proposed by employing depopulation of the lowest subbands of PQW. In this work, the theoretical analysis of an incoherent THz torch device is presented. The findings suggest that the introduction of narrower band-gap GaAsBi/GaAs rectangular quantum well within the GaAs/AlGaAs PQW can alter subbands arrangement to enable a faster depopulation mechanism exploiting LO phonon scattering. The calculated radiative power spectra show the increase of oscillator strength between the rearranged subbands of PQW due to the added GaAsBi rectangular potential. The increased intersubband radiative transition probability can lead to an efficient compact incoherent THz source – THz torch.

Third-Harmonic Generation in Special Parabolic Quantum Wells

2013 ◽  
Vol 760-762 ◽  
pp. 392-396
Author(s):  
You Bin Yu
Keyword(s):  
Quantum Well ◽  
Density Matrix ◽  
Quantum Wells ◽  
Harmonic Generation ◽  
Third Harmonic Generation ◽  
Third Harmonic ◽  
The Third ◽  
Compact Density ◽  
Asymmetric Quantum ◽  
Parabolic Quantum Wells

Third-harmonic generation in a special asymmetric quantum well is investigated. The third-harmonic generation coefficient is carried out by applying compact-density-matrix method. The numerical results are presented for a GaAs/AlGaAs asymmetric quantum well. The very large third-harmonic generation coefficient is obtained in this quantum well. Moreover, the third-harmonic generation coefficient dependents on the quantum well parameters are investigated, respectively.

scholarly journals Influence of phonon confinement on the optically detected electrophonon resonance linewidth in parabolic quantum wells

2017 ◽  
Vol 126 (1B) ◽  
Author(s):  
Nguyen Dinh Hien
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Optical Phonon ◽  
Large Range ◽  
Phonon Confinement ◽  
Resonance Linewidth ◽  
Numerical Result ◽  
Optically Detected ◽  
Parabolic Quantum Wells

We investigate the influence of optical phonon confinement described by Huang-Zhu (HZ) model on the optically detected electrophonon resonance (ODEPR) effect and ODEPR linewidth (ODEPRLW) in parabolic quantum wells (PQW) by using the operator projection. The obtained numerical result for the GaAs/AlAs parabolic quantum well shows that the ODEPR linewidths depend on the well's confinement frequency. Besides, in the two cases of confined and bulk phonons, the linewidth (LW) increases with the increase of confinement frequency. Furthermore, in the large range of the confinement frequency, the influence of phonon confinement plays an important role and cannot be neglected in considering the ODEPR linewidth.

scholarly journals The Calculation of the Ettingshausen Coefficient in Quantum Wells under the Influence of Confined Phonons (for Electron – confined Optical Phonon Scattering)

2019 ◽  
Vol 35 (2) ◽  
Author(s):  
Nguyen Thi Lam Quynh ◽  
Cao Thi Vi Ba ◽  
Nguyen Quang Bau
Keyword(s):  
Magnetic Field ◽  
Kinetic Equation ◽  
Quantum Well ◽  
Quantum Wells ◽  
Quantum Number ◽  
Optical Phonon ◽  
Phonon Scattering ◽  
Resonance Condition ◽  
Constant Electric Field ◽  
Quantum Kinetic Equation

Abstract: In this paper, we have used the method of quantum kinetic equation to calculate the analytic expression for Ettingshausen coefficient (EC) under the influence of confined phonon. We considered a quantum well in the presence of constant electric field, magnetic field and electromagnetic wave (EMW) with assumption that electron – confined optical phonon (OP) scattering is essential. The EC obtained depends on many quantities in a complicated way such as temperature, magnetic field, frequency or amplitude of EMW and m - quantum number which specify confined OP. Numerical results for GaAs/GaAsAl quantum well (QW) have displayed clearly the differences in comparison with both cases of bulk semiconductor and unconfined phonon. The result of examining the EC’s dependence on magnetic field shows that quantum number m changes resonance condition; m not only makes the increase in the number of resonance peak but also changes the position of peaks. When m is set to zero, we get the results that corresponds to unconfined OP. Keywords: Quantum well, Ettingshausen effect, Quantum kinetic equation, confined optical phonons.

scholarly journals Influence of phonon confinement on the optically detected electrophonon resonance linewidth in parabolic quantum wells

2017 ◽  
Vol 126 (1B) ◽  
pp. 5
Author(s):  
Nguyen Dinh Hien
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Optical Phonon ◽  
Large Range ◽  
Phonon Confinement ◽  
Resonance Linewidth ◽  
Numerical Result ◽  
Optically Detected ◽  
Parabolic Quantum Wells

We investigate the influence of optical phonon confinement described by Huang-Zhu (HZ) model on the optically detected electrophonon resonance (ODEPR) effect and ODEPR linewidth (ODEPRLW) in parabolic quantum wells (PQW) by using the operator projection. The obtained numerical result for the GaAs/AlAs parabolic quantum well shows that the ODEPR linewidths depend on the well's confinement frequency. Besides, in the two cases of confined and bulk phonons, the linewidth (LW) increases with the increase of confinement frequency. Furthermore, in the large range of the confinement frequency, the influence of phonon confinement plays an important role and cannot be neglected in considering the ODEPR linewidth.

Characterization of GaAs/AlGaAs quantum wells and quantum wires by chemical lattice imaging

1994 ◽  
Vol 52 ◽  
pp. 736-737
Author(s):  
A. Carlsson ◽  
J.-O. Malm ◽  
A. Gustafsson
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Vapour Phase ◽  
Quantitative Information ◽  
Lattice Imaging ◽  
Vapour Phase Epitaxy ◽  
Metalorganic Vapour Phase Epitaxy ◽  
High Resolution Images

In this study a quantum well/quantum wire (QW/QWR) structure grown on a grating of V-grooves has been characterized by a technique related to chemical lattice imaging. This technique makes it possible to extract quantitative information from high resolution images.The QW/QWR structure was grown on a GaAs substrate patterned with a grating of V-grooves. The growth rate was approximately three monolayers per second without growth interruption at the interfaces. On this substrate a barrier of nominally Al0.35 Ga0.65 As was deposited to a thickness of approximately 300 nm using metalorganic vapour phase epitaxy . On top of the Al0.35Ga0.65As barrier a 3.5 nm GaAs quantum well was deposited and to conclude the structure an additional approximate 300 nm Al0.35Ga0.65 As was deposited. The GaAs QW deposited in this manner turns out to be significantly thicker at the bottom of the grooves giving a QWR running along the grooves. During the growth of the barriers an approximately 30 nm wide Ga-rich region is formed at the bottom of the grooves giving a Ga-rich stripe extending from the bottom of each groove to the surface.

Characterisation of multilayer materials using a position-sensitive atom probe

1990 ◽  
Vol 48 (4) ◽  
pp. 624-625
Author(s):  
RAD Mackenzie ◽  
G D W Smith ◽  
A. Cerezo ◽  
J A Liddle ◽  
CRM Grovenor ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Spatial Information ◽  
Chemical Vapour ◽  
Atom Probe ◽  
Organic Chemical ◽  
Growth Stages ◽  
Multiple Quantum ◽  
Quartz Wool ◽  
Position Sensitive

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Asymmetric Ge/SiGe coupled quantum well modulators

Nanophotonics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1765-1773
Author(s):  
Yi Zhang ◽  
Jianfeng Gao ◽  
Senbiao Qin ◽  
Ming Cheng ◽  
Kang Wang ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Quantum Well ◽  
Quantum Wells ◽  
High Speed ◽  
Low Voltage ◽  
Extinction Ratio ◽  
High Frequency Response ◽  
Modulation Format ◽  
Silicon Photonic ◽  
Coupled Quantum Well

Abstract We design and demonstrate an asymmetric Ge/SiGe coupled quantum well (CQW) waveguide modulator for both intensity and phase modulation with a low bias voltage in silicon photonic integration. The asymmetric CQWs consisting of two quantum wells with different widths are employed as the active region to enhance the electro-optical characteristics of the device by controlling the coupling of the wave functions. The fabricated device can realize 5 dB extinction ratio at 1446 nm and 1.4 × 10−3 electrorefractive index variation at 1530 nm with the associated modulation efficiency V π L π of 0.055 V cm under 1 V reverse bias. The 3 dB bandwidth for high frequency response is 27 GHz under 1 V bias and the energy consumption per bit is less than 100 fJ/bit. The proposed device offers a pathway towards a low voltage, low energy consumption, high speed and compact modulator for silicon photonic integrated devices, as well as opens possibilities for achieving advanced modulation format in a more compact and simple frame.

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