Localized States in Electron-Irradiated GaAs

1991 ◽  
Vol 235 ◽  
Author(s):  
S. D. Kouimtzi ◽  
C. Melidis ◽  
C. Achtlleos
Keyword(s):  
Frequency Dependence ◽  
Electron Irradiation ◽  
Localized States ◽  
Variable Range Hopping ◽  
Defect Band ◽  
Variable Range ◽  
Sufficient Degree ◽  
Degree Of Damage ◽  
Band Tailing

ABSTRACTBand tailing produced by electron irradiation of n-type GaAs at helium temperatures is studied. It has been observed that conductance in the band tailing occurs via localized states as evidenced by the observation of a conductance having a frequency dependence of the form σ⊥ωs where ≈ 1.Sufficient degree of damage induces variable range hopping, σ ∝ exp (-b/Tl/4) in a defect band. The frequency dependence of the conductivity in this band is very weak.

Processing and Characterization of Amorphous Copper Oxide Thin Films Prepared by Reactive Magnetron Sputtering

2018 ◽  
Vol 775 ◽  
pp. 238-245 ◽  
Author(s):  
Thitinai Gaewdang ◽  
Ngamnit Wongcharoen
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Magnetron Sputtering ◽  
Copper Oxide ◽  
Flow Rate ◽  
Localized States ◽  
Positive Sign ◽  
Variable Range Hopping ◽  
Variable Range ◽  
Deposited Films

In this paper, copper oxide (CuOx) thin films with amorphous phase were prepared on glass substrates by reactive dc magnetron sputtering. The influence of the flow rate of O2 on the structural, optical and electrical properties of the as-deposited films was systematically studied. XRD revealed that the as-deposited films remained amorphous in the whole range of adjusted oxygen flow rate. Surface morphology and nanoparticle size of the films were observed by AFM. Electrical resistivity and Hall effect measurements were performed on the films with van der Pauw configuration. The positive sign of the Hall coefficient confirmed the p-type conductivity in all studied films. From temperature-dependent electrical conductivity of the films prepared at R(O2) of 1.5 sccm, it was show that three types of behavior can be expected, nearest-neighbor hopping at high temperature range (200-300 K), the Mott variable range hopping at low temperature (110-190 K) and Efros-Shklovskii variable range hopping at very low temperature (65-100 K). Some important parameters corresponding to Mott-VRH and ES-VRH like density of localized states near the Fermi level, localization length, degree of disorder, hopping distance and hopping energy were determined. These parameters would be helpful for optimizing the performance of photovoltaic applications.

Charge transport through localized states in sputtered amorphous silicon suboxides

2001 ◽  
Vol 666 ◽  
Author(s):  
J.J. van Hapert ◽  
N. Tomozeiu ◽  
E.E. van Faassen ◽  
A.M. Vredenberg ◽  
F.H.P.M. Habraken
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Rf Magnetron Sputtering ◽  
Quantitative Information ◽  
Thin Layers ◽  
Localized States ◽  
Variable Range Hopping ◽  
Defect States ◽  
Variable Range ◽  
Spin Resonance

ABSTRACTUsing an RF magnetron sputtering technique, thin layers (∼500 nm) of amorphous silicon suboxides (a-SiOx) were deposited, with oxygen/silicon ratios x ranging from 0 to 1.8. These layers contain a large density (1020−1021 cm−3) of, mostly silicon dangling bond, defect states. The level of conduction decreases several orders of magnitude with increasing x. The temperature dependence of the DC conductivity showed that the variable range hopping conduction mechanism is dominant for all x, over the temperature range 30- 330 K. In this mechanism the extent of localization and density of states around the Fermi level determine the conductance. We conclude that the decrease in conductance with increasing oxygen content must, for a large part, be due to a variation in the localization, since Electron Spin Resonance (ESR) measurements showed no decrease in defect density with increasing x. We performed DC conduction measurements at both low and high electric field strengths, showing phenomena, which are consistently desribed within the variable range hopping (VRH) model. These measurements allow the extraction of quantitative information, concerning both the localization and the density of the states involved in the hopping process.

The frequency dependence of variable range hopping

1977 ◽  
Vol 39 (2) ◽  
pp. 615-620 ◽  
Author(s):  
R. M. Hill
Keyword(s):  
Frequency Dependence ◽  
Variable Range Hopping ◽  
Variable Range

Hopping Conduction in Structures with Ge Nanoclusters Grown on Oxidized Si (001)

2016 ◽  
Vol 39 ◽  
pp. 178-188
Author(s):  
Vladimir Lysenko ◽  
Y.V. Gomeniuk ◽  
Valeriya N. Kudina ◽  
Nikolay Garbar ◽  
Sergey Kondratenko ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Fermi Level ◽  
Transport Mechanism ◽  
Surface Conductivity ◽  
Localized States ◽  
Band Width ◽  
Planar Geometry ◽  
Hopping Conduction ◽  
Variable Range Hopping ◽  
Variable Range

Conductivity and capacitance in structures with Ge nanoclusters grown on oxidized Si (001) with different morphology have been investigated for the temperature range 120-290 K and frequencies 1 kHz-1MHz in co-planar geometry. It was found that structures exhibited T-1/3 conductivity dependence. The Mott’s variable range hopping through quasi-band of localized states at the Fermi level of Ge nanoclusters and their interfaces was found to be the dominant transport mechanism in the surface conductivity channel. The quasi-band width depends of surface morphology varying in the range 110-130 meV, while the middle of the band is located at Ev+140 meV. The peak of reduced conductivity and capacitance were observed under conditions when Fermi level is in the middle of this band.

Variable-range hopping conductivity and structure of density of localized states in LaMnO3+δunder pressure

2006 ◽  
Vol 18 (45) ◽  
pp. 10291-10302 ◽  
Author(s):  
R Laiho ◽  
K G Lisunov ◽  
E Lähderanta ◽  
M L Shubnikov ◽  
Yu P Stepanov ◽  
...  
Keyword(s):  
Localized States ◽  
Variable Range Hopping ◽  
Hopping Conductivity ◽  
Variable Range ◽  
Density Of Localized States

Frequency Dependence of Hopping Conductance in Crystalline Electron Irradiated Semiconductors

1990 ◽  
Vol 209 ◽  
Author(s):  
S.D. Kouimtzi
Keyword(s):  
Temperature Dependence ◽  
Frequency Dependence ◽  
Effective Mass ◽  
Low Temperatures ◽  
Activation Energies ◽  
Low Doses ◽  
Variable Range Hopping ◽  
Variable Range ◽  
Correlated Barrier Hopping ◽  
Hopping Conductance

ABSTRACTExtensive irradiations were carried on crystalline semiconductors InSb, GaAs and InAs. At low temperatures the frequency dependence of the conductivity is observed to be sublinear (σαωs). where s<1. The dependence of s on both the degree of the induced damage and on temperature is studied and discussed in terms of the quatum mechanical tunnelling and of correlated barrier hopping mechanisms.At fairly low doses of irradiation activated conductance is observed with s having a weak temperature dependence. As the degree of damage is further increased conduction at helium temperatures takes place by variable range hopping, σαexp(-b/T1/4). The constant b is observed to depend on the effective mass for different semiconductors.At higher temperatures activated conduction is observed again. The observed activation energies E are Eg 1/4 <E<Eg 1/2 and we believe they could represent hopping of single and double carriers.

Variable range hopping via a small number of localized states in nanometer scale MOSFETs

1992 ◽  
Vol 263 (1-3) ◽  
pp. 409-414 ◽  
Author(s):  
C. de Graaf ◽  
J.W.G. Wildöer ◽  
J. Caro ◽  
S. Radelaar ◽  
K. Heyers
Keyword(s):  
Localized States ◽  
Nanometer Scale ◽  
Variable Range Hopping ◽  
Variable Range

scholarly journals Особенности частотной зависимости проводимости неупорядоченных полупроводников в области перехода к режиму с постоянной длиной прыжка

2018 ◽  
Vol 52 (2) ◽  
pp. 161
Author(s):  
М.А. Ормонт ◽  
И.П. Звягин
Keyword(s):  
Frequency Dependence ◽  
High Frequency ◽  
Rapid Decrease ◽  
Resonance Integral ◽  
Variable Range Hopping ◽  
Exponential Factor ◽  
Electron States ◽  
The Real ◽  
Hopping Conductivity ◽  
Variable Range

AbstractThe effect of hybridization of electron states on the high-frequency conductivity of disordered semiconductors is studied. It is shown that the dependence of the pre-exponential factor of the resonance integral on the intercenter separation in a pair determines the abruptness of the change in conductivity mechanisms near the transition of the frequency dependence of the real part of the conductivity σ_1(ω) from sublinear to quadratic. The abruptness of the change of the conductivity regimes is associated with a rapid decrease in hopping distance with increasing frequency near the transition, which leads to a substantial relative decrease in the contribution from the phononless conductivity component in the variable-range hopping regime with increasing frequency and transition to the fixed-range hopping conductivity regime.

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