Quantum wires in strained silicon quantum wells on tilted substrates

2000 ◽  
Vol 28 (5-6) ◽  
pp. 369-376 ◽  
Author(s):  
M.J. Rack ◽  
T.J. Thornton ◽  
D.K. Ferry
Keyword(s):  
Quantum Wells ◽  
Quantum Wires ◽  
Strained Silicon

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.

Ultrafast Carrier Dynamics, Optical Amplification, and Lasing in Nanocrystal Quantum Dots

MRS Bulletin ◽  
2001 ◽  
Vol 26 (12) ◽  
pp. 998-1004 ◽  
Author(s):  
Victor I. Klimov ◽  
Moungi G. Bawendi
Keyword(s):  
Quantum Dots ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Electronic States ◽  
Three Dimensions ◽  
Band Edge ◽  
Lasing Threshold ◽  
Wide Energy Range ◽  
Band Edge Emission ◽  
Edge States

Semiconductor materials are widely used in both optically and electrically pumped lasers. The use of semiconductor quantum wells (QWs) as optical-gain media has resulted in important advances in laser technology. QWs have a two-dimensional, step-like density of electronic states that is nonzero at the band edge, enabling a higher concentration of carriers to contribute to the band-edge emission and leading to a reduced lasing threshold, improved temperature stability, and a narrower emission line. A further enhancement in the density of the band-edge states and an associated reduction in the lasing threshold are in principle possible using quantum wires and quantum dots (QDs), in which the confinement is in two and three dimensions, respectively. In very small dots, the spacing of the electronic states is much greater than the available thermal energy (strong confinement), inhibiting thermal depopulation of the lowest electronic states. This effect should result in a lasing threshold that is temperatureinsensitive at an excitation level of only 1 electron-hole (e-h) pair per dot on average. Additionally, QDs in the strongconfinement regime have an emission wavelength that is a pronounced function of size, adding the advantage of continuous spectral tunability over a wide energy range simply by changing the size of the dots.

scholarly journals Quantum conductance staircase of holes in silicon nanosandwiches

2019 ◽  
Vol 20 (2) ◽  
pp. 81-98
Author(s):  
N. T. Bagraev ◽  
L. E. Klyachkin ◽  
A. M. Malyarenko ◽  
V. S. Khromov
Keyword(s):  
Kinetic Energy ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Energy Gap ◽  
Point Contact ◽  
Quantum Conductance ◽  
One Dimensional ◽  
Drastic Increase ◽  
Quantum Point ◽  
The One

The results of studying the quantum conductance staircase of holes in one−dimensional channels obtained by the split−gate method inside silicon nanosandwiches that are the ultra−narrow quantum well confined by the delta barriers heavily doped with boron on the n−type Si (100) surface are reported. Since the silicon quantum wells studied are ultra−narrow (~2 nm) and confined by the delta barriers that consist of the negative−U dipole boron centers, the quantized conductance of one−dimensional channels is observed at relatively high temperatures (T > 77 K). Further, the current−voltage characteristic of the quantum conductance staircase is studied in relation to the kinetic energy of holes and their sheet density in the quantum wells. The results show that the quantum conductance staircase of holes in p−Si quantum wires is caused by independent contributions of the one−dimensional (1D) subbands of the heavy and light holes; these contributions manifest themselves in the study of square−section quantum wires in the doubling of the quantum−step height (G0 = 4e2/h), except for the first step (G0 = 2e2/h) due to the absence of degeneracy of the lower 1D subband. An analysis of the heights of the first and second quantum steps indicates that there is a spontaneous spin polarization of the heavy and light holes, which emphasizes the very important role of exchange interaction in the processes of 1D transport of individual charge carriers. In addition, the field−related inhibition of the quantum conductance staircase is demonstrated in the situation when the energy of the field−induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split−gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of holes is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. In the concluding section of this paper we present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the silicon nanosandwiches prepared within frameworks of the Hall. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, Vxy, to a maximum of 4e2/h. In addition to the standard plateau, 2e2/h, the variations of the Vxy voltage appear to exhibit the fractional forms of the quantum conductance staircase with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

scholarly journals Thomas-Fermi method for computing the electron spectrum and wave functions of highly doped quantum wires in n-Si

2015 ◽  
Vol 28 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Volodymyr Grimalsky ◽  
Outmane Oubram ◽  
Svetlana Koshevaya ◽  
Christian Castrejon-Martinez
Keyword(s):  
Quantum Wells ◽  
Electron Spectrum ◽  
Quantum Wires ◽  
Wave Functions ◽  
Variation Method ◽  
Hamiltonian Matrix ◽  
Electron Mass ◽  
Dinger Equation ◽  
Effective Electron ◽  
Thomas Fermi

The application of the Thomas-Fermi method to calculate the electron spectrum in quantum wells formed by highly doped n-Si quantum wires is presented under finite temperatures where the many-body effects, like exchange, are taken into account. The electron potential energy is calculated initially from a single equation. Then the electron energy sub-levels and the wave functions within the potential well are simulated from the Schr?dinger equation. For axially symmetric wave functions the shooting method has been used. Two methods have been applied to solve the Schr?dinger equation in the case of the anisotropic effective electron mass, the variation method and the iteration procedure for the eigenvectors of the Hamiltonian matrix.

Minigaps in strained silicon quantum wells on tilted substrates

1999 ◽  
Vol 17 (4) ◽  
pp. 1757 ◽  
Author(s):  
T. J. Thornton ◽  
F. Ge ◽  
A. Andresen ◽  
D. Pivin ◽  
J. Bird ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Strained Silicon

Absorption and Emission of Light in Quantum Structures

2020 ◽  
pp. 343-418
Author(s):  
Vurgaftman Igor
Keyword(s):  
Quantum Wells ◽  
Radiative Recombination ◽  
Quantum Wires ◽  
Incident Light ◽  
Optical Gain ◽  
Two Dimensional ◽  
Intersubband Transitions ◽  
Recombination Rates ◽  
Zinc Blende ◽  
Two Dimensional Materials

This chapter shows how to calculate the absorption coefficient, optical gain, and radiative recombination rates in quantum wells and superlattices. A detailed treatment of both interband and intersubband transitions is presented, and their differences and similarities are considered in detail. The optical properties of wurtzite quantum wells and zinc-blende quantum wires and dots are also discussed. Finally, the interaction of excitonic transitions with incident light in quantum wells is considered as a model for other two-dimensional materials.

Scattering Rates in a Semiconductor Heterostructure: The Electron–Phonon Coupling

1998 ◽  
Vol 12 (16n17) ◽  
pp. 1719-1728 ◽  
Author(s):  
F. Comas ◽  
F. Castro ◽  
J. L. Gondar
Keyword(s):  
Quantum Wells ◽  
Quantum Wires ◽  
Phenomenological Theory ◽  
Applied Theory ◽  
Airy Functions ◽  
Electron Phonon Interaction ◽  
Semiconductor Heterostructure ◽  
Electron Phonon Coupling ◽  
The Subject ◽  
Scattering Rates

We investigate Scattering-Rates due to the electron–phonon interaction in a Semiconductor Heterostructure (SH) on the basis of a phenomenological theory for Polar Optical Phonons (POP) in semiconductor nanostructures which was proposed in the latter times. The applied theory has led to a plausible description of POP in Quantum-Wells, Quantum-Wires and Quantum-Dots. Using this theory we find an explicit expression for the electron–phonon Hamiltonian with direct application to a SH. Scattering Rates are calculated by applying this Hamiltonian and also a realistic wave-function for the electron states (using Airy functions) is considered. The obtained results are discussed in detail and compared with previous works on the subject.

POLAR INTERFACE-OPTICAL VIBRATIONAL SPECTRA IN A WURTZITE GaN/AlN RECTANGULAR QUANTUM WIRE

2006 ◽  
Vol 13 (01) ◽  
pp. 75-80 ◽  
Author(s):  
L. ZHANG
Keyword(s):  
Quantum Wells ◽  
Quantum Wire ◽  
Quantum Wires ◽  
Uniaxial Crystal ◽  
Wave Number ◽  
Phonon Modes ◽  
Crystal Model ◽  
Limited Frequency ◽  
Dielectric Continuum ◽  
Dielectric Continuum Model

Under the dielectric continuum model and Loudon's uniaxial crystal model, the interface optical (IO) phonon modes in a quasi-one-dimensional (Q1D) wurtzite rectangular quantum wire are deduced and analyzed. Numerical calculation on a wurtzite GaN/AlN rectangular wurtzite quantum wire was performed. Results reveal that the dispersion frequencies of IO modes sensitively depend on the geometric structures of the Q1D wurtzite rectangular quantum wires. The degenerating behavior of the IO phonon modes in the Q1D wurtzite rectangular quantum wire has been clearly observed for small free wave number kz in z-direction. The limited frequency behaviors of IO modes have been analyzed deeply, and detailed comparisons with those in wurtzite planar quantum wells and cylindrical quantum wires are also done. Moreover, once the anisotropy of the wurtzite material has been ignored, the present theories can be naturally reduced to the situation of Q1D cubic rectangular quantum wire systems.

Cryogenic field effect transistors using strained silicon quantum wells in Si:SiGe heterostructures grown by APCVD

2001 ◽  
Vol 87 (3) ◽  
pp. 277-281 ◽  
Author(s):  
M.J Rack ◽  
T.J Thornton ◽  
D.K Ferry ◽  
Jeff Roberts ◽  
Richard C Westhoff ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Strained Silicon
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