Density of states determination from steady-state photocarrier grating measurements

Schmidt, Javier Alejandro; Longeaud, Christophe

doi:10.1063/1.1818732

Cited by 9 publications

(6 citation statements)

References 9 publications

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“…In recent publications we have shown that it is possible to deduce some part of the DOS distribution, interacting with the majority carriers, from the value of ␤ taken at large grating periods ͑␤ lim ͒. 6,7 We obtained the following relation:…”

Section: The Above Expression Closely Resembles Expression ͑1͒mentioning

confidence: 86%

Determination of semiconductor band gap state parameters from photoconductivity measurements. II. Experimental results

2006

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In this paper we apply various photoconductivity techniques to study different types of semiconductors. These methods are the modulated photocurrent, the steady-state photocarrier grating, and the steady-state photoconductivity techniques, and they are used to investigate a chromium-doped gallium arsenide crystal and different hydrogenated amorphous silicon thin films. First, we briefly recall what information on the material transport parameters can be extracted from the results of these various techniques. Second, we experimentally put into evidence the links existing between these apparently very dissimilar techniques by applying them first to a GaAs:Cr crystal and finally to three hydrogenated amorphous silicon samples prepared under different conditions. For this latter material, we show that the density of states distribution, the electron capture cross sections of the states-even that of the valence band tail-and the electron extended-states mobility can be obtained from the comparison of the results of these techniques. We conclude by showing that, by introducing these parameters into a numerical simulation, we can reproduce the behaviors experimentally observed for all the photoconductivity techniques.

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Section: The Above Expression Closely Resembles Expression ͑1͒mentioning

confidence: 86%

Determination of semiconductor band gap state parameters from photoconductivity measurements. II. Experimental results

2006

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“…( 10) we do not obtain directly the density of states from the experimental data, but rather the quantity N(E tn ) Â c n / l n . This quantity is also obtained from the modulated photocurrent (MPC) technique performed in the high frequency range and from the recently proposed method to extract the DOS from SSPG measurements [17,18]. Thus, the validity of the c-DOS determination can be confirmed by comparing it to the MPC-DOS and SSPG-DOS obtained on the same a-Si : H sample by using the same standard values for c n and l n .…”

Section: Methodsmentioning

confidence: 95%

Light-intensity dependence of the steady-state photoconductivity used to estimate the density of states in the gap of intrinsic semiconductors

2005

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“…The main drawback of the second group of methods is that the DOS is only obtained over a limited energy range. In a recent publication 14 the authors presented a new method belonging to the second category, based on steady-state photocurrent grating ͑SSPG͒ measurements. In this work we discuss the method in more detail, presenting new experimental results for hydrogenated amorphous silicon samples.…”

Section: Introductionmentioning

confidence: 99%

“…To our knowledge, no attempts to derive the density of localized states directly from the application of a reconstruction formula to SSPG measurements had been presented until our recent paper. 14 This work is organized as follows. In Sec.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the steady-state photocarrier grating method for the determination of the density of states in semiconductors

Schmidt

Longeaud

2005

Phys. Rev. B

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In this paper we present a complete theoretical analysis of the steady-state photocarrier grating ͑SSPG͒ method, starting from the generalized equations that describe charge transport and recombination under grating conditions. The analytical solution of these equations and the application of simplifying assumptions leads to a very simple formula relating the density of states ͑DOS͒ at the quasi-Fermi level for trapped electrons to the SSPG signal at large grating periods. By means of numerical calculations reproducing the experimental SSPG curves we test our method for DOS determination. We examine previous theoretical descriptions of the SSPG experiment, illustrating the case when measurements are performed at different illumination intensities. We propose a procedure to estimate the minority-carriers mobility-lifetime product from SSPG curves, introducing a correction to the commonly applied formula. We illustrate the usefulness of our technique for determining the DOS in the gap of intrinsic semiconductors, and we underline its limitations when applied to hydrogenated amorphous silicon. We propose an experimental procedure that improves the accuracy of the SSPG-DOS reconstruction. Finally, we test experimentally this new method by comparing the DOS obtained from SSPG and modulated photocurrent measurements performed on the same samples. The experimental DOS obtained from both methods are in very good agreement.

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Density of states determination from steady-state photocarrier grating measurements

Cited by 9 publications

References 9 publications

Determination of semiconductor band gap state parameters from photoconductivity measurements. II. Experimental results

Determination of semiconductor band gap state parameters from photoconductivity measurements. II. Experimental results

Light-intensity dependence of the steady-state photoconductivity used to estimate the density of states in the gap of intrinsic semiconductors

Analysis of the steady-state photocarrier grating method for the determination of the density of states in semiconductors

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