The Extended State Mobility in Amorphous Silicon Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
P.M. Fauchet ◽  
R. Vanderhaghen ◽  
A. Mourchid ◽  
D. Hulin
Keyword(s):  
Amorphous Silicon ◽  
Effective Mass ◽  
Alloy Composition ◽  
Amorphous Semiconductors ◽  
Extended State ◽  
Silicon Alloys ◽  
Time Resolved ◽  
Free Carriers ◽  
Extended States ◽  
Scattering Time

ABSTRACTThe total scattering time of free carriers injected optically in the extended states of amorphous semiconductors has been measured using the techniques of femtosecond time-resolved spectroscopy. We find that this scattering time is less than 1 femtosecond, independent of alloy composition (a-Si:H, a-Si,Ge:H, a-Si,C:H) and temperature (from 77 K to 400 K). The extended state mobility deduced from the measurement of the scattering time and of the effective mass is approximately 6 cm2/Vs. A model is proposed to explain these results

Computer Modelling of Non-Equilibrium Multiple-Trapping and Hopping Transport in Amorphous Semiconductors

2005 ◽  
Vol 862 ◽  
Author(s):  
C. Main ◽  
J. M. Marshall ◽  
S. Reynolds ◽  
M.J. Rose ◽  
R. Brüggemann
Keyword(s):  
Computer Modelling ◽  
Stochastic Matrix ◽  
Computational Procedure ◽  
Amorphous Semiconductors ◽  
Extended State ◽  
Hopping Transport ◽  
Multiple Trapping ◽  
Extended States ◽  
Localised States ◽  
Gap States

AbstractIn this paper we demonstrate a simple computational procedure for the simulation of transport in a disordered semiconductor in which both multi-trapping and hopping processes are occurring simultaneously. We base the simulation on earlier work on hopping transport, which used a Monte-Carlo method. Using the same model concepts, we now employ a stochastic matrix approach to speed computation, and include also multi-trapping transitions between localised and extended states. We use the simulation to study the relative contributions of extended state conduction (with multi-trapping) and hopping conduction (via localised states) to transient photocurrents, for various distributions of localised gap states, and as a function of temperature. The implications of our findings for the interpretation of transient photocurrents are examined.

Ultrafast Dynamics of Photoexcitations in HWCVD Hydrogenated Amorphous Silicon Alloys

2000 ◽  
Vol 609 ◽  
Author(s):  
J.E. Young ◽  
B.P. Nelson ◽  
S.L. Dexheimer
Keyword(s):  
Amorphous Silicon ◽  
Pump Pulse ◽  
Strong Dependence ◽  
Hydrogenated Amorphous Silicon ◽  
Excitation Density ◽  
Band Tail ◽  
Silicon Alloys ◽  
Bimolecular Recombination ◽  
Extended States ◽  
Hydrogenated Amorphous

ABSTRACTWe present femtosecond studies of carrier dynamics in hydrogenated amorphous silicon-germanium alloys grown by the recently developed hot-wire assisted chemical vapor deposition (HWCVD) technique, which is promising for producing high-quality device-grade materials. We have used wavelength-resolved femtosecond pump-probe techniques, in which an intense pump pulse excites carriers in the sample and a time-delayed probe pulse measures the resulting change in optical properties as a function of time delay following the pump pulse, to study the dynamics of photoexcitations in these materials. Femtosecond dynamics measurements have been carried out on thin film samples under experimental conditions with varying sensitivity to carriers in extended states or in band tail states. The relaxation dynamics of carriers associated with extended states show a strong dependence on excitation density and follow a bimolecular recombination law, consistent with a number of earlier studies on related amorphous materials. In contrast, measurements involving carriers excited directly into band tail states reveal significantly altered dynamics, characterized by a marked deviation from simple bimolecular recombination at short times.

Free Carrier Lifetime in a-Si,Ge:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
D.A. Young ◽  
P.M. Fauchek ◽  
Y.M. Liu ◽  
W.L. Nighan ◽  
C.M. Fortmann
Keyword(s):  
Amorphous Silicon ◽  
Time Domain ◽  
Silicon Germanium ◽  
Free Electron Laser ◽  
Carrier Lifetime ◽  
Free Carrier ◽  
Time Resolved ◽  
Pump And Probe ◽  
Extended States ◽  
Amorphous Silicon Germanium

ABSTRACTThe lifetime of carriers injected optically in the extended states of amorphous silicon-germanium alloys has been measured by time-resolved pump and probe optical techniques using either a femtosecond dye laser or a picosecond free electron laser. When Ninj > 1018 cm-3, the lifetime of the carriers is in the picosecond time domain. Our results are comparable to what we have observed previously in a-Si:H and very recently in a-Si,C:H. There are two lifetime regimes: at high densities, the recombination is bimolecular and nonradiative, whereas at lower densities, the recombination tends to be monomolecular but still nonradiative. The origin of these lifetimes is discussed.

Photoconductivité dans l'alliage GaAsxSb1−x en présence d'un champ magnétique

1974 ◽  
Vol 52 (8) ◽  
pp. 743-747 ◽  
Author(s):  
A. Filion ◽  
E. Fortin
Keyword(s):  
Magnetic Fields ◽  
Band Gap ◽  
Effective Mass ◽  
Alloy Composition ◽  
Longitudinal Optical ◽  
Optical Phonons ◽  
Champ Magnétique

The intrinsic photoconductivity of several samples of the alloy GaAsxSb1−x has been studied at 4.2 K in the presence of magnetic fields of up to 65 kG. Values for the band-gap, the reduced effective mass of the carriers, the energy of the longitudinal optical phonons across the alloy composition are deduced from the measurements.

The Structure of Ion-Implanted Amorphous Silicon

1998 ◽  
Vol 540 ◽  
Author(s):  
J. M. Gibson ◽  
J-Y. Cheng ◽  
P. Voyles ◽  
M.M.J. TREACY ◽  
D.C. Jacobson
Keyword(s):  
Amorphous Silicon ◽  
Network Model ◽  
Random Network ◽  
Amorphous Semiconductors ◽  
Range Order ◽  
Medium Range Order ◽  
Medium Range ◽  
Large Heat ◽  
Continuous Random Network ◽  
Ion Implanted

AbstractUsing fluctuation microscopy, we show that ion-implanted amorphous silicon has more medium-range order than is expected from the continuous random network model. From our previous work on evaporated and sputtered amorphous silicon, we conclude that the structure is paracrystalline, i.e. it possesses crystalline-like order which decays with distance from any point. The observation might pose an explanation for the large heat of relaxation that is evolved by ion-implanted amorphous semiconductors.

Dynamics of the creation of light-induced defects in amorphous silicon alloys

1986 ◽  
Vol 33 (4) ◽  
pp. 2512-2519 ◽  
Author(s):  
M. Hack ◽  
S. Guha ◽  
W. den Boer
Keyword(s):  
Amorphous Silicon ◽  
Silicon Alloys ◽  
The Creation ◽  
Induced Defects

Vibrational properties of amorphous silicon alloys

1981 ◽  
Vol 23 (10) ◽  
pp. 5263-5268 ◽  
Author(s):  
W. B. Pollard ◽  
J. D. Joannopoulos
Keyword(s):  
Amorphous Silicon ◽  
Vibrational Properties ◽  
Silicon Alloys

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.

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