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.

Monte-Carlo Simulation of Generation- Recombination Noise in Amorphous Semiconductors

2002 ◽  
Vol 715 ◽  
Author(s):  
R.I. Badran ◽  
C. Main ◽  
S. Reynolds
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Noise Spectrum ◽  
Amorphous Semiconductors ◽  
Analytical Models ◽  
Release Time ◽  
Trapping Time ◽  
Extended States ◽  
Gap States ◽  
Analytical Approaches

AbstractWe compare the predictions of several analytical models for conductivity fluctuations in a homogeneous semiconductor containing discrete and distributed traps, using a Monte-Carlo simulation of the relevant multi – trapping (MT) transitions. The simulation directly embodies the statistical features associated with such processes, in a simple ‘model - independent’ approach, free of approximations and assumptions. We compare the results with those of several analytical approaches. In one, the noise spectrum is assumed to reflect separately, the characteristic individual release time constants of the various trapping centers in the material. In another, the trapping time into the ensemble of electron traps is taken to be the dominant time constant, and hence, in a material such as a-Si:H, where the trapping time into tail sates is of order 1ps, this is taken to imply that this component of the conductivity noise spectrum is unobservable in practice. Our own analytical approach, incorporates coupling (albeit weak) between traps, which necessarily communicate via the extended states. Preliminary results of the simulation support our thesis, and verify that the same information is contained in the real part of the modulated photoconductivity (MPC) spectrum. A ‘full Monte’ – Carlo simulation incorporating all gap states and spatial inhomogeneities is now a priority.

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

Photoconductivity Decay in Amorphous Semiconductors

1987 ◽  
Vol 95 ◽  
Author(s):  
William Pickin ◽  
Doroteo Mendoza ◽  
Juan Carlos Alonso
Keyword(s):  
Steady State ◽  
Decay Time ◽  
Minority Carrier ◽  
Hydrogenated Amorphous Silicon ◽  
Amorphous Semiconductors ◽  
Decay Process ◽  
Intensity Dependence ◽  
Multiple Trapping ◽  
Photoconductivity Decay ◽  
Hydrogenated Amorphous

AbstractBased on modifications of the standard multiple trapping approach we present a theory of photoconductivity decay from the steady state in which explicit account is taken of the minority carrier behaviour. We use this to develop a physical understanding of the decay process. We obtain the intensity dependence of the decay time and compare it with experimental results for hydrogenated amorphous silicon.

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