The effect of a magnetic field on the impurity band density of states in the atomic limit

1982 ◽  
Vol 60 (12) ◽  
pp. 1743-1750 ◽  
Author(s):  
K. L. Liu ◽  
P. Modrak ◽  
B. Bergersen
Keyword(s):  
Magnetic Field ◽  
Density Of States ◽  
Gaussian Model ◽  
Impurity Band ◽  
Metal Insulator ◽  
Atomic Limit ◽  
Doped Silicon ◽  
Hydrogenic Model ◽  
Type Response ◽  
The Magnetic Field

A marked magnetic field dependence is found for the impurity band density of states in an idealized model of a doped semiconductor. The calculations are based on the Hubbard model in the atomic limit. We have obtained exactly the first eight moments of the distribution using a Gaussian model for the hopping integral, and the first seven moments with a hydrogenic model. A simple Zeeman type response of the spin system to the magnetic field is assumed. The predicted density of states is then obtained using a modified moment method with a trial density of states function obtained from the expected asymptotic behaviour of the distribution. Finally, we adjust the parameters of our models to correspond to phosphorous doped silicon below the metal insulator transition.

Impurity band density of states in the atomic limit

1980 ◽  
Vol 58 (8) ◽  
pp. 1142-1150 ◽  
Author(s):  
K. L. Liu ◽  
B. Bergersen ◽  
P. Modrak
Keyword(s):  
Density Of States ◽  
Gaussian Model ◽  
Impurity Band ◽  
Realistic Model ◽  
Model Calculations ◽  
Asymptotic Expressions ◽  
Atomic Limit ◽  
Diagrammatic Method ◽  
Transfer Integral ◽  
Hydrogenic Model

Model calculations are presented for the density of states in the impurity band of a semiconductor. The calculations are based on the Hubbard model in the atomic (i.e., infinite U) limit and are thus appropriate to impurity concentration below the critical one for the metal–insulator transition. No ordering of the electron spin is assumed, instead all spin configurations are taken to be equally probable. The impurity distribution is taken to be random. Calculations are carried out with a Gaussian overlap integral as a function of impurity–impurity distance and with the transfer integral obtained from hydrogenic wave function. The first seven moments of the density of states distribution of the Gaussian model and the first six moments of the hydrogenic model are calculated using a diagrammatic method. We also discuss asymptotic expressions for the distribution in the high and low density limits. Intepolation methods to reconstruct the distribution from the moments are investigated. It is believed that the methods used are suitable for generalizations to more realistic model Hamiltonians.

MATHEMATICAL MODELING OF TEMPERATURE EFFECT ON THE FAN CHART OF MAGNETOABSORPTION SPECTRUM IN SEMICONDUCTORS

2019 ◽  
pp. 104-115
Author(s):  
G. Gulyamov ◽  
U. I. Erkaboev ◽  
A. G. Gulyamov
Keyword(s):  
Mathematical Modeling ◽  
Magnetic Field ◽  
Temperature Dependence ◽  
Density Of States ◽  
Landau Levels ◽  
Joint Density ◽  
Narrow Gap ◽  
Narrow Gap Semiconductors ◽  
Dispersion Law ◽  
The Magnetic Field

The article considers the oscillations of interband magneto-optical absorption in semiconductors with the Kane dispersion law. We have compared the changes in oscillations of the joint density of states with respect to the photon energy for different Landau levels in parabolic and non-parabolic zones. An analytical expression is obtained for the oscillation of the combined density of states in narrow-gap semiconductors. We have calculated the dependence of the maximum photon energy on the magnetic field at different temperatures. A theoretical study of the band structure showed that the magnetoabsorption oscillations decrease with an increase in temperature, and the photon energies nonlinearly depend on a strong magnetic field. The article proposes a simple method for calculating the oscillation of joint density of states in a quantizing magnetic field with the non-quadratic dispersion law. The temperature dependence of the oscillations joint density of states in semiconductors with non-parabolic dispersion law is obtained. Moreover, the article studies the temperature dependence of the band gap in a strong magnetic field with the non-quadratic dispersion law. The method is applied to the research of the magnetic absorption in narrow-gap semiconductors with nonparabolic dispersion law. It is shown that as the temperature increases, Landau levels are washed away due to thermal broadening and density of states turns into a density of states without a magnetic field. Using the mathematical model, the temperature dependence of the density distribution of energy states in strong magnetic fields is considered. It is shown that the continuous spectrum of the density of states, measured at the temperature of liquid nitrogen, at low temperatures turns into discrete Landau levels. Mathematical modeling of processes using experimental values of the continuous spectrum of the density of states makes it possible to calculate discrete Landau levels. We have created the three-dimensional fan chart of magneto optical oscillations of semiconductors with considering for the joint density of energy states. For a nonquadratic dispersion law, the maximum frequency of the absorbed light and the width of the forbidden band are shown to depend nonlinearly on the magnetic field. Modeling the temperature  dependence allowed us to determine the Landau levels in semiconductors in a wide temperature spectrum. Using the proposed model, the experimental results obtained for narrow-gap semiconductors are analyzed. The theoretical results are compared with experimental results.

Dependence of the a-Si:H Defect Density of States on the Magnetic Field Profile of an Electron Cyclotron Resonance Microwave Plasma

1992 ◽  
Vol 258 ◽  
Author(s):  
F.S. Pool ◽  
J.M. Essick ◽  
Y.H. Shing ◽  
R.T. Mather
Keyword(s):  
Magnetic Field ◽  
Density Of States ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Microwave Plasma ◽  
Defect Density ◽  
Electron Cyclotron ◽  
Field Profile ◽  
Magnetic Field Profile ◽  
The Magnetic Field

ABSTRACTThe magnetic field profile of an electron cyclotron resonance (ECR) microwave plasma was systematically altered to determine subsequent effects on a-Si:H film quality. Films of a-Si:H were deposited at pressures of 0.7 mTorr and 5 mTorr with a H2/SiH4 ratio of approximately three. The mobility gap density of states ND, deposition rate and light to dark conductivity were determined for the a-Si:H films. This data was correlated to the magnetic field profile of the plasma, which was characterized by Langmuir probe measurements of the ion current density. By variation of the magnetic field profile ND could be altered by more than an order of magnitude, from 1×1016 to 1×1017 at 0.7 mTorr and 1×1016 to 5×1017 at 5 mTorr. Two deposition regimes were found to occur for the conditions of this study. Highly divergent magnetic fields resulted in poor quality a-Si:H, while for magnetic field profiles defining a more highly confined plasma, the a-Si:H was of device quality and relatively independent of the magnetic field configuration.

About the Metal-Insulator Transition in Quasicrystals

2000 ◽  
Vol 643 ◽  
Author(s):  
J. Delahaye ◽  
C. Berger ◽  
T. Grenet ◽  
G. Fourcaudot
Keyword(s):  
Magnetic Field ◽  
Fermi Level ◽  
Electronic Properties ◽  
Field Dependence ◽  
Density Of States ◽  
Disordered Systems ◽  
Magnetic Field Dependence ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Mi Transition

AbstractElectronic properties (conductivity and density of states) of quasicrystals present strong similarities with disordered semiconductor based systems on both sides of the Mott-Anderson metal-insulator (MI) transition. We revisit the conductivity of the i-AlCuFe and i-AlPdMn phases, which has temperature and magnetic field dependence characteristic of the metallic side of the transition. The i-AlPdRe ribbon samples can be on either side of the transition depending on their conductivity value. In all these i-phases, the density of states at the Fermi level EF is low. Its energy dependence close to EF is similar to disordered systems close to the MI transition where it is ascribed to effects of interactions between electrons and disorder.

Review lecture: Metal–insulator transitions

1982 ◽  
Vol 382 (1782) ◽  
pp. 1-24 ◽  
Keyword(s):  
Magnetic Field ◽  
Gate Voltage ◽  
Disordered Systems ◽  
Mixed Valence ◽  
Impurity Band ◽  
Donor Concentration ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
First Order ◽  
Or Gate

A survey is given of a variety of solids that show a metal–insulator transition. In crystals most transitions are expected to be of first order as the composition or temperature is changed; in disordered systems this is not necessarily the case. The transition in an impurity band with change of donor concentration is described, and also with change of stress, magnetic field or gate voltage. The concept of a minimum metallic conductivity is discussed, with special reference to materials of mixed valence.

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