Ambipolar Diffusion Coefficients in a-SiC:H Alloys in Steady- State and Transient Grating Measurements

Recently we have determined surprisingly large values of the ambipolar diffusion coefficient D of 3 − 9 cm2/s in amorphous silicon-based alloys and a-Si:H/a-SiC:H multilayer structures from transient grating decays in the psec time domain. The steady-state photocarrier grating method, however, resulted in much lower D values (∼10−4 cm2/s) in the same samples. Since high carrier densities of typically 1019 cm−3 are reached in the psec domain, the Einstein relation may no longer be valid. The large diffusivity of non-equilibrium carriers decreases, however, rapidly in time due to energy relaxation and carrier recombination until a stable trap occupation under steady-state condition is reached.

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Interdiffusion and Carrier Recombination in High Intensity Transient Gratings

MRS Proceedings ◽

10.1557/proc-420-723 ◽

1996 ◽

Vol 420 ◽

Cited By ~ 2

Author(s):

R. Schwarz ◽

S. Grebner ◽

C. E. Nebel ◽

M. Lanz ◽

M. Stutzmann

Keyword(s):

Steady State ◽

Amorphous Silicon ◽

Nd:Yag Laser ◽

Diffusion Coefficients ◽

High Light ◽

Near Band Edge ◽

Dispersive Transport ◽

Carrier Recombination ◽

P Type ◽

Type Sample

AbstractTransient grating (TG) experiments were performed to study carrier diffusion and recombination in amorphous silicon films (a-Si:H) at high light intensities using 8 ns pulses from a frequency-doubled Nd:YAG laser. The ambipolar diffusion coefficients reached about 10−2cm2/s, which is 2 orders of magnitude larger than the steady-state value. Similar results were obtained in intrinsic, p-, and n-doped a-Si:H films, indicating that the diffusion coefficients in all cases reflect the near band edge mobility of the slower carriers, that is holes. In particular, the p-type sample shows an initially fast, then a slow grating efficiency decay, consistent with dispersive transport.

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Evaluation of diffusion coefficients by means of an approximate steady-state condition in sedimentation velocity distributions

Analytical Biochemistry ◽

10.1016/j.ab.2015.08.017 ◽

2015 ◽

Vol 490 ◽

pp. 20-25 ◽

Cited By ~ 3

Author(s):

David J. Scott ◽

Stephen E. Harding ◽

Donald J. Winzor

Keyword(s):

Steady State ◽

Diffusion Coefficients ◽

Sedimentation Velocity ◽

State Condition ◽

Steady State Condition

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Transient grating measurements of ambipolar diffusion and carrier recombination in InGaP/lnAIP multiple quantum wells and InGaP bulk

Journal of Electronic Materials ◽

10.1007/bf03296065 ◽

1994 ◽

Vol 23 (3) ◽

pp. 359-362 ◽

Cited By ~ 7

Author(s):

M. Prasad ◽

O.E. Martinez ◽

C.S. Menoni ◽

J.J. Rocca ◽

J.L.A. Chilla ◽

...

Keyword(s):

Quantum Wells ◽

Ambipolar Diffusion ◽

Multiple Quantum Wells ◽

Multiple Quantum ◽

Transient Grating ◽

Carrier Recombination

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Lifetime Regime in the Electrically-Detected Transient Grating Method Applied to Amorphous and Microcrystalline Silicon Films

MRS Proceedings ◽

10.1557/proc-715-a20.2 ◽

2002 ◽

Vol 715 ◽

Cited By ~ 1

Author(s):

P. Sanguino ◽

M. Niehus ◽

S. Koynov ◽

P. Brogueira ◽

R. Schwarz ◽

...

Keyword(s):

Carrier Transport ◽

Analytical Calculation ◽

Chemical Vapor ◽

Silicon Films ◽

Dielectric Relaxation Time ◽

Transient Grating ◽

Minority Carrier Diffusion Length ◽

Carrier Recombination ◽

Thin Silicon ◽

Good Agreement

AbstractThe minority-carrier diffusion length in thin silicon films can be extracted from the electrically-detected transient grating method, EDTG, by a simple ambipolar analysis only in the case of lifetime dominated carrier transport. If the dielectric relaxation time, τdiel, is larger than the photocarrier response time, τR, then unexpected negative transient signals can appear in the EDTG result. Thin silicon films deposited by hot-wire chemical vapor deposition (HWCVD) near the amorphous-to-microcrystalline transition, where τR varies over a large range, appeared to be ideal candidates to study the interplay between carrier recombination and dielectric response. By modifying the ambipolar description to allow for a time-dependent carrier grating build-up and decay we can obtain a good agreement between analytical calculation and experimental results.

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Non-steady-state chloride diffusion coefficients obtained from migration and natural diffusion tests. Part II: Different experimental conditions. Joint relations

Materials and Structures ◽

10.1617/13621 ◽

2005 ◽

Vol 34 (240) ◽

pp. 323-331 ◽

Cited By ~ 1

Author(s):

M. Castellote

Keyword(s):

Steady State ◽

Diffusion Coefficients ◽

Chloride Diffusion ◽

Experimental Conditions

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Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation

Computation ◽

10.3390/computation9060065 ◽

2021 ◽

Vol 9 (6) ◽

pp. 65

Author(s):

Aditya Dewanto Hartono ◽

Kyuro Sasaki ◽

Yuichi Sugai ◽

Ronald Nguele

Keyword(s):

Heat Transfer ◽

Steady State ◽

Natural Convection ◽

Lattice Boltzmann ◽

Numerical Results ◽

Convection And Heat Transfer ◽

Steady State Condition ◽

Physical Systems ◽

Flow And Heat Transfer ◽

Computational Performance

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

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