scholarly journals Selfsimilar analysis of n-type delta-doped quasiregular GaAs quantum wells

Nova Scientia ◽  
2014 ◽  
Vol 6 (12) ◽  
pp. 162
Author(s):  
Heraclio García-Cervantes ◽  
Isaac Rodríguez-Vargas
Keyword(s):  
Electronic Structure ◽  
Quantum Wells ◽  
Tight Binding ◽  
Fibonacci Sequence ◽  
Building Blocks ◽  
Binding Model ◽  
Localized State ◽  
The Difference ◽  
Surface Green Function ◽  
Semi Empirical

We study the electronic structure of n-type delta-doped quantum wells in GaAs in which the multiple well system is built according to the Fibonacci sequence. The building blocks A and B correspond to delta-doped wells with impurities densities n2DA and n2DB, and the same well width. The Thomas-Fermi approximation, the semi-empirical sp3s* tight-binding model including spin, the Surface Green Function Matching method and the Transfer Matrix approach were implemented to obtain the confining potential, the electronic structure and the selfsimilarity of the spectrum. The fragmentation of the electronic spectra is observed whenever the building blocks A and B interact and it increases as the difference of impurities density between A and B increases as well. The wave function of the first state of the fragmented bands presents critical characteristics, this is, it is not a localized state nor a extended one as well as it has selfsimilar features. So, the quasiregular characteristics are preserved irrespective of the complexity of the system and can affect the performance of devices based on these structures

Tight-Binding Model for DNA Double Chains: Metal–Insulator Transition Due to the Formation of a Double Strand of DNA

1997 ◽  
Vol 11 (20) ◽  
pp. 2405-2423 ◽  
Author(s):  
Kazumoto Iguchi
Keyword(s):  
Electronic Structure ◽  
Finite Temperature ◽  
Deoxyribonucleic Acid ◽  
Recent Observation ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Metal Insulator Transition ◽  
Binding Model ◽  
Metal Insulator ◽  
System A

A tight-binding model is formulated for the calculation of the electronic structure of a double strand of deoxyribonucleic acid (DNA). The theory is applied to DNA with a particular structure such as the ladder and decorated ladder structures. It is found that there is a novel type of metal–insulator transitions due to the hopping anisotropy of the system. A metal-semimetal-semiconductor transition is found in the former and an effective semiconductor-metal transition at finite temperature in the latter, as the effect of base paring between two strands of DNA is increased. The latter mechanism may be responsible for explaining the Meade and Kayyem's recent observation.

scholarly journals Influence of Internal Electric Fields on the Ground Level Emission of GaN/AlGaN Multi-Quantum Wells

2000 ◽  
Vol 5 (S1) ◽  
pp. 970-976
Author(s):  
A. Bonfiglio ◽  
M. Lomascolo ◽  
G. Traetta ◽  
R. Cingolani ◽  
A. Di Carlo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Quantum Wells ◽  
Electric Fields ◽  
Tight Binding ◽  
Ground Level ◽  
Analytic Model ◽  
Tight Binding Model ◽  
Binding Model ◽  
Emission Energy ◽  
Self Consistent

The spectroscopic investigation of GaN/AlGaN quantum wells reveals that the emission energy of such structures is determined by four parameters, namely composition, well-width, strain and charge density. The experimental data obtained by varying these parameters are quantitatively explained by an analytic model based on the envelope function formalism which accounts for screening and built-in field, and by a full self-consistent tight-binding model.

Electronic Structure of Si/InAs Composite Channels

2007 ◽  
Vol 995 ◽  
Author(s):  
Marta Prada ◽  
Neerav Kharche ◽  
Gerhard Klimeck
Keyword(s):  
Electronic Structure ◽  
Quantum Well ◽  
Effective Mass ◽  
Tight Binding ◽  
Localized States ◽  
Equivalent Thickness ◽  
Binding Model ◽  
Direct Bandgap ◽  
Effective Masses ◽  
Composite Channels

AbstractElectronic structure calculations on composite channels, consisting of indium arsenide grown on the technologically relevant (001), (011) and (112)-orientated silicon surfaces are reported. The calculations are performed with NEMO 3-D, where atoms are represented explicitly in the sp3d5s* tight-binding model. The Valence Force Field (VFF) method is employed to minimize the strain. NEMO 3-D enables the calculation of localized states in the quantum well (QW) and their dispersion in the quantum well plane. From this dispersion, the bandgap, its direct or indirect in character, and the associated effective masses of the valence and conduction band can be determined. Such composite bandstructure calculations are demonstrated here for the first time. The numerical results presented here can then be included in empirical device models to estimate device performance. Pure InAs QWs create a direct bandgap material, with a relatively small gap and effective masses of about one order of magnitude smaller than for pure Si QW of equivalent thickness. Si, on the other hand, has a larger bandgap, superior thermal and mechanical properties, and a heavily invested industry. Thus heteroepitaxy of both components is expected to yield a highly optimized overall system. For samples grown along the (001) direction, Si is a direct bandgap material, and deposition of an InAs 3nm layer reduces substantially the hole effective mass and slightly the electronic mass, decreasing the magnitude of the gap. Along the (011) and (112)-growth direction, Si QWs are indirect bandgap material, and deposition of a few InAs layers suffies to make the new material a direct-bandgap heterostructure, decreasing significantly the electronic effective mass. (011) and (112) are the experimentally most relevant growth directions since they prevent heterointerface dipoles.

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