Transient modulated photocurrent studies in hydrogenated amorphous silicon: a new look at defect relaxation dynamics

Cohen, J. David; Fan, Zhengxiu

doi:10.1016/0022-3093(95)00265-0

Cited by 10 publications

(5 citation statements)

References 28 publications

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“…More recently, the sensitivity of this technique was examined by Brüggemann et al [12] by means of numerical simulation for different light absorption depths. Measurements of the MPC in a-Si:H in the sandwich sample configuration were also carried out by Amato et al [13] and Cohen and Zhong [14]. It is worth noting that in the former paper a distinct dependence of both the phase shift and the amplitude of the MPC on the exciting light wavelength was established.…”

Section: Introductionmentioning

confidence: 91%

Modulated photocurrents in a sandwich-cell structure

Grygiel

Tomaszewicz

2000

J. Phys.: Condens. Matter

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Approximate formulae describing modulated photocurrents in a sandwich configuration of sample electrodes are derived. The carrier transport is described in terms of the multiple-trapping model. The formulae refer to arbitrary spatial distribution of generated carriers. The case of exponential light absorption in the sample is considered in detail. It is shown that for limiting low and high modulation frequencies, both the amplitude and the phase shift of the photocurrent are almost independent of the light absorption coefficient. In the intermediate-frequency range, for the case of surface carrier generation, the phase shift of the photocurrent usually shows oscillations. This makes it possible to obtain the energetic density of states from a simple formula. Examples of calculated frequency dependencies of the photocurrent phase shift and amplitude are given for exponential and Gaussian trap distributions as well as for a single trap level.

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Section: Introductionmentioning

confidence: 91%

Modulated photocurrents in a sandwich-cell structure

Grygiel

Tomaszewicz

2000

J. Phys.: Condens. Matter

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“…From equation ( 13) it results that n(d) = n(0) exp(−iϕ − γ ). Thus, ϕ and γ represent, respectively, the phase and the 'damping coefficient' of the free-carrier-density wave at x = d. With these notations, formula (14) for the photocurrent takes the form of…”

Section: Expression For the Mpcmentioning

confidence: 99%

“…The spatial sensitivity of this method was then investigated numerically by Brüggemann et al [12]. The results of the MPC measurements in a sandwich-cell structure have also been given in [13,14] for a-Si:H, in [15] for copper phthalocyanine and in [16] for poly-(N-vinylcarbazole). In the papers [11,13,15] the modified Oheda theory has been utilized.…”

Section: Introductionmentioning

confidence: 99%

Modulated photocurrents in a sandwich-cell structure: II. Influence of bias illumination intensity and carrier diffusion

Tomaszewicz¹,

Grygiel²

2003

J. Phys.: Condens. Matter

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The influence of bias illumination level and carrier diffusion on the modulated photocurrents (MPCs), measured in amorphous solids in a sandwich electrode configuration, is investigated theoretically. Based on the multiple-trapping model the approximate formulae for MPCs, taking into account the mentioned physical factors, are derived. It is demonstrated that the absolute magnitude of the density of states can be determined from the MPC frequency spectra, measured at suitable bias illumination intensities. The carrier diffusion affects the MPCs solely for relatively high modulation frequencies and/or low applied voltages. The criterion for neglecting the diffusion effect is given. The corresponding frequency dependences of the photocurrent phase shift and amplitude as well as of the related quantities, calculated for the exponential trap distribution, are presented.

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“…6 However, in polycrystalline materials with columnar structure of the grains, the electronic transport, which is parallel to the substrate in coplanar configuration, differs from that in sandwich structure of the solar cell where the transport path of the photogenerated carriers is essentially perpendicular to the substrate. For such materials, it is then interesting to study the modulated photocurrent in sandwich configuration but so far, only few studies have been devoted to this point, [7][8][9][10][11] essentially in the framework of multiple-trapping model and for the case where the light excitation energy is higher than the semiconductor band gap, except works of Abe et al 8 and Mencaraglia et al, 9 where subgap light excitation has been considered.…”

Section: Introductionmentioning

confidence: 99%

Subgap modulated photocurrent spectroscopy and its application to the study of the solar cell absorber defect distributions

Djebbour

Serhan

Migan‐Dubois

et al. 2010

Journal of Applied Physics

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In this paper, a theoretical background of subgap modulated photocurrent experiment is presented. It allows the investigation of the density of states ͑DOS͒ distribution, directly from the active region of a semiconductor heterojunction device. The junction is illuminated with a modulated subgap light excitation ͑i.e., light with photon energy lower than the band gap of the active layer͒. Under specific considerations for the applied reverse bias voltage and the bias-light level, a simple theoretical relation of the imaginary part of the photocurrent versus the modulation angular frequency allows the determination of the energy profile of the gap states. This technique has been successfully applied to a Ga free Cu͑In, Ga͒Se 2 based solar cell to investigate the DOS distribution in the band gap of the absorber. Two distinct defect distributions have been exhibited in the absorber layer of the studied solar cell.

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Transient modulated photocurrent studies in hydrogenated amorphous silicon: a new look at defect relaxation dynamics

Cited by 10 publications

References 28 publications

Modulated photocurrents in a sandwich-cell structure

Modulated photocurrents in a sandwich-cell structure

Modulated photocurrents in a sandwich-cell structure: II. Influence of bias illumination intensity and carrier diffusion

Subgap modulated photocurrent spectroscopy and its application to the study of the solar cell absorber defect distributions

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