Interpretation of the conductance and capacitance frequency dependence of hydrogenated amorphous silicon Schottky barrier diodes

Viktorovitch, Pierre; Moddel, Garret

doi:10.1063/1.328319

Cited by 104 publications

(9 citation statements)

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“…Various circuit models have been proposed and applied to TFSC devices. [45][46][47][48] A practical complication is that typically one does not know a priori what range of frequency and temperature are required to allow extraction of the given parameter (i.e., deep or shallow states, free carrier density, diffusion voltage) from the measured admittance, as discussed below. The standard analysis of an abrupt p-n junction assumes a uniform space-charge density created by a spatially uniform distribution of shallow ionized donors or acceptors.…”

Section: Admittance Characterizationmentioning

confidence: 99%

“…The correct series-parallel circuit model must be used to extract these parameters from measurements. 45,47,48 Equation (18) represents the case for junction capacitance and conductance in parallel. The total admittance of the device should include the parallel combination of bulk elements C B and G B in series with the junction elements as in Figure 12.…”

Section: Admittance Characterizationmentioning

confidence: 99%

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Thin‐film solar cells: device measurements and analysis

Hegedus

Shafarman

2004

Progress in Photovoltaics

1,044

740

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Characterization of amorphous Si, CdTe, and Cu(InGa)Se 2 -based thin-film solar cells is described with focus on the deviations in device behavior from standard device models. Quantum efficiency (QE), current-voltage (J-V), and admittance measurements are reviewed with regard to aspects of interpretation unique to the thin-film solar cells. In each case, methods are presented for characterizing parasitic effects common in these solar cells in order to identify loss mechanisms and reveal fundamental device properties. Differences between these thin-film solar cells and idealized devices are largely due to a high density of defect states in the absorbing layers and to parasitic losses due to the device structure and contacts. There is also commonly a voltage-dependent photocurrent collection which affects J-V and QE measurements. The voltage and light bias dependence of these measurements can be used to diagnose specific losses. Examples of how these losses impact the QE, J-V, and admittance characterization are shown for each type of solar cell.Solar cell operation, either crystalline or thin film, can be described by identifying loss mechanisms. These can be divided into three categories. First are recombination losses which limit the open-circuit voltage V OC . Second are parasitic losses, such as series resistance, shunt conductance, and voltage-dependent current collection, which primarily impact the fill factor (FF), but can also reduce short circuit current J SC and V OC . Finally, there are optical losses which limit generation of carriers and, therefore, J SC . We focus on losses largely unique to TFSCs.Physical and electrical properties of TFSCs which cause them to have different losses from the standard 'textbook' crystalline Si (c-Si) cells include: * TFSC absorber layers have much higher absorption coefficients than c-Si so a large fraction of the photogeneration occurs near the interface and in the high field space charge region (SCR). This enables high currents, even with relatively small collection lengths; * the semiconductor films often have a range of shallow and deep defect levels or defect bands within the bandgap. These result from imperfect crystallinity or amorphous structure and from the use of low-cost materials and processes optimized for high throughput and low cost as much as for high device efficiency. This can create different recombination mechanisms than radiative band-to-band recombination commonly found in ideal crystalline semiconductor devices; * poor minority carrier lifetime, due to the above factors, leads to increased reliance on the electric field for sufficient minority carrier collection rather than diffusion alone. This often results in voltage-dependent collection of light-generated current; * TFSCs are heterojunction device structures with high densities of defect states at interfaces which can provide a path for interface recombination; * the grain boundaries in polycrystalline Cu(InGa)Se 2 and CdTe devices may act as high recombination surfaces or shunt paths. This l...

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Section: Admittance Characterizationmentioning

confidence: 99%

Section: Admittance Characterizationmentioning

confidence: 99%

Thin‐film solar cells: device measurements and analysis

Hegedus

Shafarman

2004

Progress in Photovoltaics

1,044

740

View full text Add to dashboard Cite

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“…The restriction of our experiments to zero dc bias U = 0 ascertains the validity of the equilibrium Fermi level for holes and electrons [8]. The application of a small-signal ac voltage v then causes variations of the potential p = -( y ( v ) -y ( 0 ) ) and of the space-charge density = e ( v ) -e(0) that completely express the ac disturbance and are linked analogous to (2) and (5) by p" = GIs and, in the quasistationary case, by p" -p; = P ( pp,)…”

Section: Small-signal Capacitancementioning

confidence: 74%

Capacitance of amorphous silicon pin solar cells

Pfleiderer

Rauscher

1983

Phys. Stat. Sol. (a)

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The i-region of pin solar cells on the basis of amorphous silicon provides the carrier collection. The density of (localized) states (DOS) in this region diminishes the electric field, favors recombination and limits the collection efficiency. The low-frequency capacitance of pin diodes is indicative for the DOS. The small-signal capacitance of a pin solar cell is measured in the frequency range 0.1 to lo3 H z for temperatures between 30 and 100 "C at zero dc bias. A simple diode model is suggested.It involves the assumption of constant DOS values in the p-, i-, and n-regions. These values are determined by fitting. It is shown that low-level doping of the i-region and illumination stress significantly raise the capacitance and the DOS. Das i-Gebiet von pin-Sonnenzellen aus amorphem Silizium besorgt die Sammlung der Ladungstrager. Die Dichte der (lokalisierten) Zustande (DOS) in diesem Gebiet vermindert das elektrische Feld, begiinstigt Rekombination und begrenzt den Sammelwirkungsgrad. Die Niederfrequenz-Kapazitat von pin-Dioden zeigt die DOS an. Die Kleinsignal-Kapazitiit einer pin-Sonnenzelle wird im Frequenzbereich 0,l bis los Hz fur Temperaturen zwischcn 30 und 100 "C ohne uberlagerte Gleichspannung gemessen. Ein einfnches Diodenmodell wird vorgeschlagen. Es beruht auf der Annahme konstanter DOS-Werte in den p-, i-und n-Gebieten. Diese Werte werden durch Anpassung bestimmt. Es wird gezeigt, daB schwache Dotierung des i-Gebiets und Dauerbeleuchtung Kapazitat und DOS deutlich erhohen.

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“…[22][23][24] In particular for the p-i-p device, each time a bias is applied, a transience takes place during which the carriers already existing within the intrinsic region are swept toward the p-i interfaces together, however, with many other carriers newly generated with their own characteristic time constants. [22][23][24] In particular for the p-i-p device, each time a bias is applied, a transience takes place during which the carriers already existing within the intrinsic region are swept toward the p-i interfaces together, however, with many other carriers newly generated with their own characteristic time constants.…”

Section: Resultsmentioning

confidence: 99%

Electro-optical effect in hydrogenated amorphous silicon-based waveguide-integrated p-i-p and p-i-n configurations

et al. 2013

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A p-i-p configuration of an electro-optical modulator based on hydrogenated amorphous silicon (a-Si:H) is characterized and compared with an a-Si:H based p-i-n modulator. In particular, we estimate the performances in terms of optical losses, voltage-length product, and bandwidth at λ ¼ 1550 nm for waveguide-integrated p-i-p versus p-i-n configurations. Both devices are fabricated on a silicon substrate by plasma enhanced chemical vapor deposition at low temperature ensuring the back-end integration with a CMOS microchip. We demonstrate a factor of merit for the p-i-p waveguide integrated Fabry-Perot resonator of V π × Lπ ¼ 19 V × cm allowing the design of shorter devices with respect to p-i-n structure.

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Interpretation of the conductance and capacitance frequency dependence of hydrogenated amorphous silicon Schottky barrier diodes

Cited by 104 publications

References 11 publications

Thin‐film solar cells: device measurements and analysis

Thin‐film solar cells: device measurements and analysis

Capacitance of amorphous silicon pin solar cells

Electro-optical effect in hydrogenated amorphous silicon-based waveguide-integrated p-i-p and p-i-n configurations

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