Effect of boron localized states on the conduction band transport in BxGa1−xP

2014 ◽  
Vol 105 (22) ◽  
pp. 222105 ◽  
Author(s):  
S. Petznick ◽  
L. Ostheim ◽  
P. J. Klar ◽  
S. Liebich ◽  
K. Volz ◽  
...  
Keyword(s):  
Conduction Band ◽  
Localized States

Density of Deep Bandgap States in Amorphous Silicon From the Temperature Dependence of Thin Film Transistor Current

1994 ◽  
Vol 336 ◽  
Author(s):  
T. Globus ◽  
H. C. Slade ◽  
M. Shur ◽  
M. Hack
Keyword(s):  
Thin Film ◽  
Activation Energy ◽  
Amorphous Silicon ◽  
Conduction Band ◽  
Energy Gap ◽  
Localized States ◽  
Flat Band ◽  
Gate Bias ◽  
Density Of Localized States ◽  
Wide Range

ABSTRACTWe have measured the current-voltage characteristics of amorphous silicon thin film transistors (a-Si TFTs) over a wide range of temperatures (20 to 160°C) and determined the activation energy of the channel current as a function of gate bias with emphasis on the leakage current and subthreshold regimes. We propose a new method for estimating the density of localized states (DOS) from the dependence of the derivative of activation energy with respect to gate bias. This differential technique does not require knowledge of the flat-band voltage (VFB) and does not incorporate integration over gate bias. Using this Method, we have characterized the density of localized states with energies in the range 0.15–1.2 eV from the bottom of the conduction band and have found a wide peak in the DOS in the range of 0.8–0.95 eV below the conduction band. We have also observed that the DOS peak in the lower half of the bandgap increases in magnitude and shifts towards the conduction band as a result of thermal and bias stress. We also measured an overall increase in the DOS in the upper half of the energy gap and an additional peak, centered at 0.2 eV below the conduction band, which appear due to the applied stress. These results are in qualitative agreement with the defect pool Model [1,2].

Photoconductivity study of amorphous CdTe

1977 ◽  
Vol 55 (3) ◽  
pp. 265-269 ◽  
Author(s):  
R. T. S. Shiah ◽  
D. E. Brodie ◽  
P. C. Eastman
Keyword(s):  
Light Intensity ◽  
Fermi Level ◽  
Conduction Band ◽  
Localized States ◽  
Effective Density ◽  
Transition Rates ◽  
Mobility Edge ◽  
Energy Parameters ◽  
Density Of Localized States ◽  
Mobility Gap

Photoconductivity measurements as a function of light intensity and temperature for amorphous CdTe are analyzed on the basis of the Mott and Davis model and some ideas of the Arnoldussen, Bube, Fagen, and Holmberg model. Energy parameters within the mobility gap of amorphous CdTe were evaluated. The effective density of localized states is found to be 1017and 1019 per cm3 per eV near the valence and conduction band edges respectively. The localized-to-localized recombination transition rates are also given. The dark Fermi level is found to be 0.54 eV above the valence mobility edge. Localized states extend into the mobility gap 0.37 eV from the valence mobility edge. These results are consistent with earlier measurements by Ng, Webb, and Brodie.

scholarly journals C-, N-, S-, and F-Doped Anatase TiO2 (101) with Oxygen Vacancies: Photocatalysts Active in the Visible Region

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Julio César González-Torres ◽  
Enrique Poulain ◽  
Víctor Domínguez-Soria ◽  
Raúl García-Cruz ◽  
Oscar Olvera-Neria
Keyword(s):  
Visible Light ◽  
Conduction Band ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Visible Region ◽  
Charge Carriers ◽  
Localized States ◽  
Similar Process ◽  
Visible Radiation ◽  
C Doping

Anatase TiO2 presents a large bandgap of 3.2 eV, which inhibits the use of visible light radiation (λ > 387 nm) for generating charge carriers. We studied the activation of TiO2 (101) anatase with visible light by doping with C, N, S, and F atoms. For this purpose, density functional theory and the Hubbard U approach are used. We identify two ways for activating the TiO2 with visible light. The first mechanism is broadening the valence or conduction band; for example, in the S-doped TiO2 (101) system, the valence band is broadened. A similar process can occur in the conduction band when the undercoordinated Ti atoms are exposed on the TiO2 (101) surface. The second mechanism, and more efficient for activating the anatase, is to generate localized states in the gap: N-doping creates localized empty states in the bandgap. For C-doping, the surface TiO2 (101) presents a “cleaner” gap than the bulk TiO2, resulting in fewer recombination centers. The dopant valence electrons determine the number and position of the localized states in the bandgap. The formation of charge carriers with visible light is highly favored by the oxygen vacancies on TiO2 (101). The catalytic activity of C-doping using visible radiation can be explained by its high absorption intensity generated by oxygen vacancies on the surface. The intensity of the visible absorption spectrum of doped TiO2 (101) follows the order: C > N > F > S dopant.

The effect of negative capacitance in varistor structure on the basis of its models with voltage drop on the intergranular interlayer

2015 ◽  
Vol 11 (4) ◽  
pp. 598-615 ◽  
Author(s):  
Alexander Sergeevich Tonkoshkur ◽  
Alexander Vladimirovich Ivanchenko
Keyword(s):  
Conduction Band ◽  
Potential Barrier ◽  
Voltage Drop ◽  
Voltage Characteristic ◽  
Localized States ◽  
Negative Capacitance ◽  
Nonlinear Conductivity ◽  
Content Type ◽  
Wide Range ◽  
Capacitance Voltage

Purpose – The purpose of this paper is modeling the effect of negative capacitance in the capacitance-voltage characteristic of the intergranular potential barrier of varistor structure. Design/methodology/approach – The modeling of the capacitance-voltage characteristic of the intergranular barrier in metal oxide varistor ceramics is based on the development of the algorithm. It includes all the known mechanisms of electrotransfer in a wide range of voltages and currents, and also takes into account the voltage drop on the intergranular interlayer of intergranular potential barrier. Findings – The models and algorithms for calculating the capacitance-voltage characteristics of a single intergranular potential barrier with the use of the most established understanding used at the interpretation of the nonlinear conductivity intergranular barrier are developed. The results of the capacitance-voltage characteristics modeling correspond to the existing understanding of the electrical properties on the ac current varistor ceramics are based on zinc oxide. The model allows to predict the behavior of varistors on the alternating current (voltage). Originality/value – It is established that the recharge of the surface localized states occurs when a voltage is applied to the varistor structure, it can lead to a relaxation decrease in the width of the potential barrier overcome by tunneling electrons in the field emission from the conduction band of the one crystallite in the conduction band of the other crystallite and thus to the current backlog of applied voltage on the phase (i.e. the expression of the negative capacitance effect).

Numerical Simulation of the Transient Photoconductivity in A-SI:H as a Function of the Excitation Density

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Feist ◽  
M. Kunst
Keyword(s):  
Density Dependence ◽  
Conduction Band ◽  
Dynamic Equilibrium ◽  
Localized States ◽  
Time Range ◽  
Excitation Density ◽  
Band Tail ◽  
Transient Photoconductivity ◽  
Excess Electrons ◽  
Short Time

ABSTRACTThe dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter kBB of 10−8cm3/s. This model leads to a decay faster than experimentally observed in the time range from 40ns to 1 μs. A variation of the recombination model is presented that gives a better fit for the longer time range still showing the correct excitation density dependence in the short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.

LOCALIZED STATES AND BAND STRUCTURE

1972 ◽  
Vol 33 (C3) ◽  
pp. C3-21-C3-25 ◽  
Author(s):  
F. BASSANI
Keyword(s):  
Band Structure ◽  
Localized States
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