Computer simulation of the photoluminescence decay at the GaAs-electrolyte junction. 2. The influence of the excitation intensity under depletion layer conditions

Krueger, O.; Jung, Ch.; Gajewski, H.

doi:10.1021/j100099a033

Cited by 7 publications

(10 citation statements)

References 4 publications

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“…An underlying assumption in the analysis of the data leading to these very large apparent charge-transfer rate constants is that the real-time photoluminescence decay data is sensitive to, and can be used to evaluate quantitatively, the values of S min and k ct for a semiconductor under the experimental conditions of interest. This assumption appears to be in contradiction to prior experimental work, which has demonstrated that the transient photoluminescence decay signals, , and the transient photocurrent signals, , of a strongly depleted semiconductor/liquid interface under low- or moderate-level injection conditions are insensitive to the value of k ct under most experimentally accessible conditions.…”

Section: Introductioncontrasting

confidence: 84%

“…Each capture coefficient is related to the product of the thermal velocity, v , of the carrier in the solid and the capture cross section, σ, for each kinetic event such that From the principle of detailed balance, it can be shown that the values of n 1,s , p 1,s , n 1 , and p 1 are definable as − , and or, in general, at any point in the solid and where N c is the effective density of states in the conduction band, E f is the Fermi level energy, and E c is the energy of the conduction band. All energies, E c , E v , and E f , are functions of position in the semiconductor. ,,,− …”

Section: Physical Representation Of the Semiconductor/liquid Contact ...mentioning

confidence: 99%

“…The Shockley−Read−Hall recombination rate describing the trapping kinetics in the bulk of the semiconductor has a form similar to eq 12, but incorporates parameters that describe the carrier concentrations and trapping rate constants in the bulk of the solid. Equations similar to eqs 10−12 have been used previously to provide boundary conditions for the simulation of photoluminescence decay data using ToSCA. ,,, Such steady-state equations do not, however, adequately describe the photoluminescence decay dynamics under all of the conditions of concern in this study. Under steady-state conditions, that is, when the lifetime for the change of trap occupancy is small compared to all other electrical and thermal carrier generation and capture processes, the steady-state Shockley−Read−Hall treatment provides an accurate description of the recombination kinetics for both carrier types with respect to midgap recombination sites. − ,, However, in circumstances where the carrier concentration changes rapidly, the SRH model is no longer justifiable because the trap states can become saturated. , In addition, the SRH model will not be valid when trap occupancy favors one carrier over another .…”

Section: Physical Representation Of the Semiconductor/liquid Contact ...mentioning

confidence: 99%

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Conditions Under Which Heterogeneous Charge-Transfer Rate Constants Can Be Extracted from Transient Photoluminescence Decay Data of Semiconductor/Liquid Contacts As Determined by Two-Dimensional Transport Modeling

et al. 1998

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An extensive series of digital simulations of the decay dynamics of photoexcited charge carriers at a semiconductor/liquid interface has been performed using the two-dimensional simulation code ToSCA. ToSCA treats majority and minority carrier capture processes separately and incorporates field-dependent carrier mobility terms. These features produce dramatic differences in the output parameters obtained when fitting experimental data with ToSCA relative to those obtained by fitting such data with prior, less complete, simulations. The simulations revealed that for a typical (n-type in our example) InP electrode in contact with outer-sphere redox reagents dissolved in the liquid phase the photoluminescence decays were generally insensitive to the value of the minority carrier charge-transfer rate constant, k ht . Instead, diffusion and driftinduced separation of photogenerated carriers in the space-charge layer of the semiconductor dominated the time decay of the observed luminescence signal under most experimentally accessible conditions. Values of k ht and of the minority carrier low-level surface recombination velocity, S p , could be obtained from an analysis of the photoluminescence decays only when the following restricted sets of conditions were satisfied simultaneously: 10 1 cm s -1 e S p e 10 5 cm s -1 , 10 -18 cm 4 s -1 e k ht e 10 -15 cm 4 s -1 , and the electrode potential, E, was in the region 0 < E < +0.15 V relative to the flat-band potential of the n-type semiconductor/ liquid interface. The simulations demonstrated that it was not possible to extract a "field dependence" of the charge-transfer rate constant when the semiconductor/liquid contact was maintained in reverse bias (E g +0.15 V vs the flat-band potential) and was subjected to light pulses that produced low or moderate carrier injection levels. Under such conditions, the photoluminescence decay dynamics were dominated by driftinduced charge separation in the space-charge layer of the semiconductor. Under high-level injection conditions, no "field dependence" could be observed because the majority of the photoluminescence decay dynamics occurred near the flat-band condition, so the value of the band bending in the semiconductor under dark, equilibrium conditions had negligible influence on the luminescence transients produced by a high-intensity laser pulse. Additionally, comparison between one-dimensional and two-dimensional simulations showed that use of one-dimensional simulation routines to extract S p and k ht values from experimental data obtained using focused laser beam excitation can lead to severe overestimates of interfacial charge-transfer rates.

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Section: Introductioncontrasting

confidence: 84%

Section: Physical Representation Of the Semiconductor/liquid Contact ...mentioning

confidence: 99%

Section: Physical Representation Of the Semiconductor/liquid Contact ...mentioning

confidence: 99%

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Conditions Under Which Heterogeneous Charge-Transfer Rate Constants Can Be Extracted from Transient Photoluminescence Decay Data of Semiconductor/Liquid Contacts As Determined by Two-Dimensional Transport Modeling

et al. 1998

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“…Surface recombination via midgap states is often assumed to be a facile process which is independent of system parameters such as excitation power and applied potential. − Under these circumstances, the surface is a sink for minority carriers, and band unbending is difficult to achieve because the facile loss mechanism increases the required injection rate even further. Yet this picture is inconsistent with recent studies of the GaAs/electrolyte interface, ,− which suggest that the detailed kinetics of surface recombination has a significant influence on carrier dynamics near the GaAs/electrolyte surface.…”

Section: Introductioncontrasting

confidence: 59%

“…[18][19][20] Under these circumstances, the surface is a sink for minority carriers, and band unbending is difficult to achieve because the facile loss mechanism increases the required injection rate even further. Yet this picture is inconsistent with recent studies of the GaAs/ electrolyte interface, 16, [21][22][23][24][25][26][27][28][29] which suggest that the detailed kinetics of surface recombination has a significant influence on carrier dynamics near the GaAs/electrolyte surface.…”

Section: Introductioncontrasting

confidence: 58%

Surface Recombination Kinetics at the GaAs/Electrolyte Interface via Photoluminescence Efficiency Measurements

1998

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Photoluminescence from GaAs/electrolyte junctions can provide detailed information concerning the kinetics of surface recombination. Here we present the results of a study of picosecond laser excited photoluminescence from the n-GaAs/Na 2 S electrolyte junction. We have developed a model for the dependence of the photoluminescence efficiency (PLE) on the surface minority carrier trapping rate following photoexcitation with a short light pulse. The model indicates that the functional dependence of the PLE on the surface minority carrier trapping rate is identical to that under CW excitation. The PLE from the n-GaAs/Na 2 S junction is shown to depend strongly on the excitation intensity, which we attribute to surface trap state filling. We have used our model to measure the surface minority trapping velocity as a function of excitation power at the flat band potential. From these measurements we conclude that the residence time of minority carriers within the trap states is on the order of microseconds, which is 3 orders of magnitude longer than the bulk minority carrier lifetime.

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Semiconductor Photoelectrochemistry

Anz¹,

Fajardo²,

Royea³

et al. 2002

Characterization of Materials

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This article discusses methods and experimental protocols in semiconductor electrochemistry. The basic principles that govern the energetics and kinetics of charge flow at a semiconductor‐liquid contact are discussed. The principal electrochemical techniques of photocurrent and photovoltage measurements used to obtain important interfacial energetic and kinetic quantities of such contacts are then described in detail. After this basic description of concepts and methods in semiconductor electrochemistry, methods for characterizing the optical, electrical, and chemical properties of semiconductors through use of the electrochemical properties of semiconductor‐liquid interfaces are described. The latter part of this unit focuses on methods that provide information primarily on the properties of the semiconductor surface and on the semiconductor‐liquid junction. In some cases, the semiconductor‐liquid junction provides a convenient method for measuring properties of the bulk semiconductor that can only be accessed with great difficulty through other techniques; in other cases, the semiconductor‐liquid contact enables measurement of properties that cannot be determined using other methods. Due to the extensive amount of background material and the interdisciplinary nature of work in this field, the discussion is not intended to be exhaustive, and the references cited in the various protocols should be consulted for further information. This article covers the following methods in semiconductor electrochemistry: Photoconductor/photovoltage measurements Measurement of semiconductor band gaps using semiconductor‐liquid interfaces Diffusion length determination using semiconductor‐liquid contacts Differential capacitance measurements of semiconductor‐liquid contacts Transient decay dynamics of semiconductor‐liquid contacts Measurement of surface recombination velocity using time‐resolved microwave conductivity Electrochemical photocapacitance spectroscopy Laser spot scanning methods at semiconductor‐liquid contacts Flat‐band potential measurements of semiconductor‐liquid interface Time‐resolved photoluminescence spectroscopy to determine interfacial charge transfer kinetic parameters Steady‐state J‐E data to determine kinetic properties of semiconductor‐liquid interfaces.

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Computer simulation of the photoluminescence decay at the GaAs-electrolyte junction. 2. The influence of the excitation intensity under depletion layer conditions

Cited by 7 publications

References 4 publications

Conditions Under Which Heterogeneous Charge-Transfer Rate Constants Can Be Extracted from Transient Photoluminescence Decay Data of Semiconductor/Liquid Contacts As Determined by Two-Dimensional Transport Modeling

Conditions Under Which Heterogeneous Charge-Transfer Rate Constants Can Be Extracted from Transient Photoluminescence Decay Data of Semiconductor/Liquid Contacts As Determined by Two-Dimensional Transport Modeling

Surface Recombination Kinetics at the GaAs/Electrolyte Interface via Photoluminescence Efficiency Measurements

Semiconductor Photoelectrochemistry

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