PHOTORESPONSE TIME AND DENSITY OF LOCALIZED STATES IN THE MOBILITY GAP OF a-Si:H ALLOYS PREPARED BY R.F. GLOW DISCHARGE

1981 ◽  
Vol 42 (C4) ◽  
pp. C4-609-C4-612 ◽  
Author(s):  
L. Guimarães ◽  
R. Martins ◽  
A. G. Dias
Keyword(s):  
Glow Discharge ◽  
Localized States ◽  
Density Of Localized States ◽  
Mobility Gap

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.

Density of localized states in glow-discharge a-Si1-x Cx:H

1991 ◽  
Author(s):  
Ozcan Oktu ◽  
Sandro Usala ◽  
Guy J. Adriaenssens ◽  
H. Tolunay ◽  
A. Eray
Keyword(s):  
Glow Discharge ◽  
Localized States ◽  
Density Of Localized States

Determination of Density of Localized States in Amorphous Silicon Alloys From the Low Field Conductance of Thin N-I-N Diodes

1985 ◽  
Vol 49 ◽  
Author(s):  
Michael Shur ◽  
Michael Hack
Keyword(s):  
Temperature Dependence ◽  
Amorphous Silicon ◽  
Bulk Density ◽  
Density Of States ◽  
Energy Gap ◽  
Localized States ◽  
New Technique ◽  
Silicon Alloys ◽  
Low Field ◽  
Density Of Localized States

AbstractWe describe a new technique to determine the bulk density of localized states in the energy gap of amorphous silicon alloys from the temperature dependence of the low field conductance of n-i-n diodes. This new technique allows us to determine the bulk density of states in the centre of a device, and is very straightforward, involving fewer assumptions than other established techniques. Varying the intrinsic layer thickness allows us to measure the,density of states within approximately 400 meV of midgap.We measured the temperature dependence of the low field conductance of an amorphous silicon alloy n-i-n diode with an intrinsic layer thjckness of 0.45 microns and deduced the density of localised states to be 3xlO16cm−3 eV−1 at approximately 0.5 eV below the bottom of the conduction band. We have also considered the high bias region (the space charge limited current regime) and proposed an interpolation formula which describes the current-voltage characteristics of these structures at all biases and agrees well with our computer simulation based on the solution of the complete system of transport equations.

HOPPING CONDUCTION IN POLYMERS

1994 ◽  
Vol 08 (07) ◽  
pp. 847-854 ◽  
Author(s):  
Heinz Bässler
Keyword(s):  
Charge Transport ◽  
Carrier Mobility ◽  
Localized States ◽  
Time Dependent ◽  
Hopping Conduction ◽  
Moderate Degree ◽  
Density Of Localized States ◽  
Temporal Features ◽  
Gaussian Density ◽  
Energetic Disorder

The concept of hopping within a Gaussian density of localized states introduced earlier to rationalize charge transport in random organic photoconductors is developed further to account for temporal features of time of flight (TOF) signals. At moderate degree of energetic disorder (σ/kT~3.5…4.5) there is a transport regime intermediate between dispersive and quasi-Gaussian type whose signatures are (i) universal TOF signals that can appear weakly dispersive despite yielding a well defined carrier mobility and (ii) an asymmetric propagator of the carrier packet yielding a time dependent diffusivity.

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].

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