Comparison of the dispersion parameters from time-of-flight and photo-induced midgap absorption measurements on sputtered a-Si:H

Kirby, Paul B.; Paul, William; Ray, Shaumik; Tauc, J.

doi:10.1016/0038-1098(82)90637-8

Cited by 26 publications

(4 citation statements)

References 7 publications

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“…The experimental quantities of interest can be calculated from the Green function Gij(t), which is the formal solution (1). In Laplace space the solution can be written ~i j ( p ) = G: (6, + I WiiGU) (2) with the local Green function G;, in Laplace spacep given by 'Barred' quantities are understood as configurationally averaged, keeping the initial The diffusivity Di(t) and energy relaxation function Ei(t) are given explicitly by and final sites i, j fixed, i.e. Gij = (GJij, etc.…”

Section: Theory Of Transport and Relaxation At Low Temperaturesmentioning

confidence: 99%

Theory of photoluminescence decay and electric-field-dependent energy relaxation in disordered materials at low temperature

Grünewald

Movaghar

1989

J. Phys.: Condens. Matter

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We present a systematic and exact evaluation of diffusivity, energy, photoluminescence (PL) decay and photoconduction for systems with energetic and positional disorder in thelow-temperature limit. Whereas most quantities can be calculated analytically in the long-time limit (slowing down of relaxation), the PL requires explicit calculation of the total transition probability G,(t). The problemcan be solved by a step-by-step approximation for a simplified PL model, emphasising the diffusional aspect. Finite electric fields lead to drastic modifications of relaxation laws at low temperature. We derive a formalism which can be applied with great generality in particular to amorphous semiconductors, quantumwell superlattices and disordered organic materials.

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Section: Theory Of Transport and Relaxation At Low Temperaturesmentioning

confidence: 99%

Theory of photoluminescence decay and electric-field-dependent energy relaxation in disordered materials at low temperature

Grünewald

Movaghar

1989

J. Phys.: Condens. Matter

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“…The continuous time random walk model and fractional Fokker-Planck equation predict α i = α f [10,27]. However, measured values of α i and α f are slightly different [12,30]. When they are different we choose α = α i because photoluminescence mainly decays within the transit time and the origin of discrepancy between α i and α f has not been fully understood.…”

Section: Discussionmentioning

confidence: 99%

“…In the time-of-flight experiments the transit current, I, is described by two different power law decay functions, I ∝ t −(1−α i ) (t < t tr ) and [12,30]. When they are different we choose α = α i because photoluminescence mainly decays within the transit time and the origin of discrepancy between α i and α f has not been fully understood.…”

Section: Discussionmentioning

confidence: 99%

Dispersive photoluminescence decay by geminate recombination in amorphous semiconductors

Seki¹,

Murayama²,

Tachiya³

2005

Phys. Rev. B

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The photoluminescence decay in amorphous semiconductors is described by power law t −δ at long times. The power-law decay of photoluminescence at long times is commonly observed but recent experiments have revealed that the exponent, δ ∼ 1.2 − 1.3, is smaller than the value 1.5 predicted from a geminate recombination model assuming normal diffusion. Transient currents observed in the time-of-flight experiments are highly dispersive characterized by the disorder parameter α smaller than 1. Geminate recombination rate should be influenced by the dispersive transport of charge carriers. In this paper we derive the simple relation, δ = 1 + α/2. Not only the exponent but also the amplitude of the decay calculated in this study is consistent with measured photoluminescence in a-Si:H.

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“…This analysis remains valid as long as ␣ Ͻ 1, i.e., for temperatures less than E 0 / k. In practice, the unique value of ␣ is never obtained from the two slopes at more than one temperature, [6][7][8] and the direct proportionality between ␣ and T is poorly obeyed. 8,9 Analysis of d data sets as a function of temperature or applied field has led to other proposed distributions, 8,10-13 but they generally covered only a small part of the tail-state energy range or accounted for changes in just one of the experimental parameters.…”

Section: Time-of-flight Transient Photoconductivitymentioning

confidence: 99%

Nonexponential distributions of tail states in hydrogenated amorphous silicon

2005

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The analysis of the time-of-flight ͑TOF͒ photocurrent transients that leads to the identification of exponential band tails in hydrogenated amorphous silicon ͑a-Si:H͒, also predicts an electric-field dependence of the carrier drift mobilities. To account for a-Si:H samples, prepared in different ways and deposition rates, that do not show this field dependence of the drift mobility, general analytic expressions for the trap-limited-bandtransport TOF signals were examined with nonexponential tail-state distributions. It is found that the use of a Gaussian tail-state component makes it possible to match the experimental curves when a field-independent mobility is measured. For samples that are prepared at, or close to, the conditions used for the plasma-enhanced chemical vapor deposition of standard "device-quality" a-Si:H, a purely exponential distribution does afford a good description of the experimental data. However, for samples prepared at high deposition rates in an expanding thermal plasma, or for polymorphous silicon, a significant Gaussian component is resolved in the tail-state distribution. These components can be linked to the presence in the amorphous matrix of nanoscopic more ordered silicon regions.

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Comparison of the dispersion parameters from time-of-flight and photo-induced midgap absorption measurements on sputtered a-Si:H

Cited by 26 publications

References 7 publications

Theory of photoluminescence decay and electric-field-dependent energy relaxation in disordered materials at low temperature

Theory of photoluminescence decay and electric-field-dependent energy relaxation in disordered materials at low temperature

Dispersive photoluminescence decay by geminate recombination in amorphous semiconductors

Nonexponential distributions of tail states in hydrogenated amorphous silicon

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