Zero Valley Splitting at Zero Magnetic Field for Strained Si/SiGe Quantum Wells

2007 ◽  
Vol 1017 ◽  
Author(s):  
Seungwon Lee ◽  
Paul von Allmen
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Conduction Band ◽  
Brillouin Zone ◽  
Tilt Angle ◽  
Tight Binding ◽  
Direct Consequence ◽  
Zero Magnetic Field ◽  
Strained Si ◽  
Valley Splitting

AbstractThe electronic structure for a strained silicon quantum well grown on a tilted SiGe substrate is calculated using an empirical tight-binding method. For a zero substrate tilt angle the two lowest minima of the conduction band define a non-zero valley splitting at the center of the Brillouin zone. A finite tilt angle for the substrate results in displacing the two lowest conduction band minima to finite k0 and -k0 in the Brillouin zone with equal energy. The vanishing of the valley splitting for quantum wells grown on tilted substrates is found to be a direct consequence of the periodicity of the steps at the interfaces between the quantum well and the buffer materials.

Bandstructure Near Misfit Dislocations in Si Quantum Wells

1998 ◽  
Vol 4 (S2) ◽  
pp. 794-795
Author(s):  
P.E. Batson
Keyword(s):  
Quantum Wells ◽  
Conduction Band ◽  
Electron Mobility ◽  
Axial Strain ◽  
Strain Relaxation ◽  
Local Potential ◽  
Misfit Dislocations ◽  
High Electron ◽  
Strained Si ◽  
Growth Interface

High electron mobility structures have been built for several years now using strained silicon layers grown on SixGe(1-x) with x in the 25-40% range. In these structures, a thin layer of silicon is grown between layers of unstrained GeSi alloy. Matching of the two lattices in the plane of growth produces a bi-axial strain in the silicon, splitting the conduction band and providing light electron levels for enhanced mobility. If the silicon channel becomes too thick, strain relaxation can occur by injection of misfit dislocations at the growth interface between the silicon and GeSi alloy. The strain field of these dislocations then gives rise to a local potential variation that limits electron mobility in the strained Si channel. This study seeks to verify this mechanism by measuring the absolute conduction band shifts which track the local potential near the misfit dislocations.

Electron Subband Levels of n-Type δ-Doped Quantum Wells under In-Plane Magnetic Fields

1997 ◽  
Vol 11 (09) ◽  
pp. 1195-1207
Author(s):  
E. K. Takahashi ◽  
A. T. Lino ◽  
L. M. R. Scolfaro
Keyword(s):  
Magnetic Field ◽  
Electronic Structure ◽  
Magnetic Fields ◽  
Quantum Well ◽  
Quantum Wells ◽  
Conduction Band ◽  
Electron Energy ◽  
Self Consistent ◽  
Plane Direction ◽  
The Magnetic Field

Self-consistent calculations of the electronic structure of center n-δ-doped GaAs/Al x Ga 1-x As quantum wells under in-plane magnetic fields are presented. The field B is varied up to 20 Tesla for different quantum well widths L w and sheet donor concentrations N D . The magnetic field produces noticeable changes in the energy dispersions along an in-plane direction perpendicular to B. The effects of B are more pronounced for higher electronic subbands. It is found that the diamagnetic shifts increase with increasing L w and/or N D . Contrarily to what has been observed in modulation-doped quantum wells, in these δ-doped systems the electron energy dispersions keep the single conduction band minimum at the center of the Brillouin zone even for intense magnetic fields.

Electronic Properties of Ultrathin Isoelectronic Intralayers in Semiconductors

1991 ◽  
Vol 240 ◽  
Author(s):  
K. A. Mäder ◽  
A. Baldereschi
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Green’S Function ◽  
Electronic Properties ◽  
Green's Function ◽  
Tight Binding ◽  
Function Approach ◽  
Diamond Structure ◽  
Two Dimensional ◽  
Host Materials

ABSTRACTAn empirical tight-binding Koster-Slater approach is used to determine the electronic properties of ultrathin“quantum wells”in semiconducting host materials of the zincblende or diamond structure. The“quantum well”is viewed as a giant two-dimensional isoelectronic impurity, and treated in a perturbational Green's function approach. We present results on the AlAs/GaAs and on the InP/InAs systems.

Conduction edge strain splitting in Ge-Si quantum wells using EELS

1993 ◽  
Vol 51 ◽  
pp. 816-817
Author(s):  
P.E. Batson ◽  
J.F. Morar
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Conduction Band ◽  
Lattice Mismatch ◽  
Axial Strain ◽  
Band Edge ◽  
Reference Level ◽  
Conduction Band Edge ◽  
Type I ◽  
Quantum Well Structures

Ge/Si quantum well structures show a high hole mobility as the heavy hole bands are shifted to lower energy under bi-axial strain produced by lattice mismatch between the well and the Si substrate. This strain can also split and shift the conduction band edge in the well to below that of Si, producing a Type I quantum well capable of photo-luminescence. In previous work, we have shown that the conduction bandstructure can be obtained using EELS in the relaxed Ge/Si alloy system. Also, we have noticed that the heterojunction band offset can be obtained from EELS because the Si 2p core level is a constant energy reference level throughout the alloy composition. In this report, we show that a detailed fitting of the shape of the Si L2,3 edge can obtain the bi-axial strain splitting of the conduction band edge as a function of position inside a quantum well. This information can then be correlated with annular dark field images of the cross sectioned well.

scholarly journals Multiscale theory of valley splitting in the conduction band of a quantum well

2008 ◽  
Vol 77 (19) ◽  
Author(s):  
Sucismita Chutia ◽  
S. N. Coppersmith ◽  
Mark Friesen
Keyword(s):  
Quantum Well ◽  
Conduction Band ◽  
Valley Splitting

BULK NONPARABOLIC EFFECTIVE MASS APPLIED TO CALCULATION OF LANDAU LEVEL ENERGY AND COMPARISON WITH CYCLOTRON RESONANCE IN InGaAs/InAlAs QUANTUM WELLS

2004 ◽  
Vol 18 (27n29) ◽  
pp. 3835-3838
Author(s):  
NOBUO KOTERA ◽  
KOICHI TANAKA ◽  
NOBORU MIURA
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Effective Mass ◽  
Conduction Band ◽  
Electron Energy ◽  
Landau Level ◽  
Cyclotron Resonance ◽  
Energy Calculation ◽  
Level Energy ◽  
Band Nonparabolicity

Observation of band nonparabolicity is difficult because the electron energy in conduction band cannot be controlled widely. Using quantization energy in quantum well (QW) where the eigen energy is changed by QW thickness, nonparabolic effective mass inside a single QW of InGaAs was determined recently, up to 0.5 eV above bandedge. The dependence of effective mass on energy was analyzed and applied to calculate Landau level energy. Calculation fit well with cyclotron resonance experiments. Coupling between skew and normal cyclotron resonance was identified by this analysis.

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.

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