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1
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Effect of Zn:Se Ratio on the Properties of Sprayed ZnSe Thin Films

100%
Öztaş M., Bedir M., Bakkaloğlu Ö., Ormancı R.
Acta Physica Polonica A
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2005
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vol. 107
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issue 3
525-534
EN
The effect of Zn:Se ratio on the photoconducting properties of ZnSe thin films has been studied. The ZnSe thin films have been deposited onto glass substrates by the spray pyrolysis method, the substrate temperature kept at 430ºC using mixed aqueous solutions of ZnCl_2 and SeO_2 with different Zn:Se ratios. Their electrical, structural, and photoconductivity properties have been studied. The values of optical bandgap have been determined from the absorption spectra.
2
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Studies of Transport Properties of Single Layer Devices Based on the Polyazomethine Thin Films

100%
Weszka J., Domański M., Jurusik J., Hajduk B., Chwastek M., Bednarski H.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
936-938
EN
This work reports results of studies on transport properties of single-layer devices based on polyazomethine thin films with different metal electrodes. Recorded I-V characteristics of Au-PPI-Au and Au-PPI-Al structures were analyzed in detail. It appears that I-V characteristics of Au-PPI-Au structures are consistent with the Mott-Gurney law with the mobility value of 2× 10^{-6} cm^2/(V s). Relatively low current in Au-PPI-Al devices is attributed to high value of the Schottky barrier and/or due to low density of longer conjugated segments in polyazomethine thin films.
3
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Gain Studies on Photoconductors Made on Partly Compensated GaAs

100%
Riesz F.
Acta Physica Polonica A
|
1995
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vol. 87
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issue 2
373-376
EN
The gain behavior of GaAs photoconductors realized on the partly com­pensated channel of a MESFET is studied. The gain versus light power de­pendence hints at the domination of the bimolecular recombination and the trap-mediated gain, and only a minor role of the surface photovoltaic ef­fect. The possible correlation between dark current and gain mechanism is pointed out.
4
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Influence of Temperature and Illumination on the Electrical Characteristics of Nanocrystalline Cu_2S Based Heterojunctions for Photodetector Application

100%
Soliman H., Farag A., Saadeldin M., Sawaby K.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 6
1688-1693
EN
In this work, heterojunctions of Cu_2S/p-Si were prepared by high vacuum thermal evaporation technique and examined as a photodetector structure. The dark current-voltage (I-V) characteristics of the heterojunctions measured at different temperatures ranging from 303 to 373 K were investigated. The predominant conduction mechanisms, series resistance, ideality factor and potential barrier height were determined. The downward curvature at sufficiently large voltages in the I-V characteristics is caused by the effect of series resistance R_{s}. The ideality factor obtained from I-V characteristics is larger than unity which can be attributed to the presence of a thin interfacial insulator layer between the metal and semiconductor. The photocurrent properties of the device under reverse bias using various illuminations were also explored for checking the validity of photodetector application of the studied device. The responsivity of light for the device under reverse bias confirms that the Cu_2S/p-Si heterojunctions are valid for photodetector application. Moreover, these results suggest that the fabricated diode can be used for optical sensor applications. The capacitance-voltage characteristics of diode were also investigated at high frequency of 1 MHz.
5
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Stability of Diodes with Poly(3-hexylthiophene) and Polyazomethines Thin Organic Layer

100%
Bednarski H., Gąsiorowski J., Domański M., Hajduk B., Jurusik J., Jarząbek B., Weszka J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1083-1086
EN
Herein we report results of studies on stability of diodes based on organic semiconductors such as poly (3-hexylthiophene) (P3HT) and soluble derivative of polyazomethine poly(1,4-(2,5-bisoctyloxy phenylenemethylidynenitrilo)-1,4-phenylenenitrilomethylidyne), (BOO-PPI). Both polymers were deposited on glass/ITO substrate with or without covering with blocking layer: poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) and finished with Al back electrode. Prepared devices were studied by monitoring their electrical conductivity under nitrogen atmosphere and ambient air conditions. Under nitrogen atmosphere a marked influence of presence of the blocking layer on the diodes electrical conductivity was revealed. The P3HT diodes prepared without PEDOT:PSS thin film shown quick degradation, whereas presence of these layers stabilizes electrical conductivity in these devices. Inversely, the PPI based diodes without the PEDOT:PSS revealed stable conducting properties, while corresponding diodes with PEDOT:PSS layer showed degradation traces of their conducting properties.
6
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Photoelectromagnetic Investigations of Graphene

80%
Nowak M., Solecka B., Jesionek M.
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vol. 126
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issue 5
1104-1106
EN
The photoelectromagnetic investigations of graphene has been performed using noncontact technique. The dependence of photoelectromagnetic response on magnetic field induction, illumination intensity for different photon energies, and frequency of illumination chopping is presented. We anticipate our paper to be a starting point for investigations of carrier diffusion length in this material. Such investigations should be essential for development of graphene electronic and optoelectronic devices.
7
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Charge Carrier Transport in Non-Homogeneous MDMO-PPV Polymer

80%
Kažukauskas V., Pranaitis M., Janonis V.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
128-130
EN
By thermally stimulated currents we have investigated carrier transport and trapping in [poly-(2-methoxyl, 5-(3,77dimethyloctyloxy)] paraphenylenevinylene (MDMO-PPV). To assure selective excitation of the defect states the spectral width of the exciting light was varied from 1.77 eV up to 3.1 eV. The thermally stimulated current curves were shown to be a superposition of carrier generation from trapping states and thermally stimulated mobility growth. The extrinsic excitation resulted in 0.16 eV photoconductivity effective activation energy values, which decreased down to 0.05 eV for the intrinsic excitation. The deeper states with activation energies of 0.28-0.3 eV and 0.8-0.85 eV were identified, too. The results are direct indication of distributed in energy trapping and transport states with the standard deviation of the density of states of about 0.015 eV.
8
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Gain and Dark Current Studies on Planar Photodetectors Made on Annealed GaAs-on-Si

80%
Riesz F., Tuven V. V., Varrio J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
889-892
EN
Interdigital, planar photodetectors were fabricated from annealed GaAs/Si heterostructures grown by molecular beam epitaxy using alloyed AuGe/Ni and non-alloyed Cr/Au contacts. The dark current and optical gain of the Cr/Au devices is higher than that of the AuGe/Ni devices. Contact degradation due to annealing and a p-like background doping consistently explains our data. The gain-optical power relationship follows a power law with an exponent close to -1.
9
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Content available

Tuning of Spectral Sensitivity of AlGaN/GaN UV Detector

80%
Korona K., Drabińska A., Trajnerowicz A., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
675-681
EN
GaN/AlGaN photodetector that exhibits new interesting property is presented. Its spectral sensitivity depends upon bias voltage. Under positive or low negative bias the detector is sensitive mainly to the ultrafiolet radiation absorbed by AlGaN layer 3.7-3.8 eV. Under negative bias U_B below -4 V, the detector is sensitive mainly to the radiation absorbed by GaN (3.4-3.6 eV). The effect can be explained based on numerical calculations of the electric field and potential profiles of this structure. The damping of GaN signal is attributed to activity of 2D electron gas formed on the GaN/AlGaN interface by spontaneous polarization. The reappearing of the signal is attributed to tunneling of holes through AlGaN, stimulated by a high electric field.
10
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Investigation of Localized Electric Field in the Type-II InAs/GaAsSb/GaAs Structure

80%
Lee S., Kim J., Yoon S., Kim Y., Lee S., Honsberg C.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 5
1213-1216
EN
The effect of localized electric field (F) was investigated in the type-II InAs/GaAsSb/GaAs structures. To compare type-I to type-II, two types of samples with different Sb contents was grown by molecular beam epitaxy, whose Sb contents are 3% (type-I) and 16% (type-II), respectively. In the both samples, we performed excitation power dependent-photoreflectance at 10 K and the result showed that the period of the Franz-Keldysh oscillation, revealed above the band gap (E_{g}) of GaAs, was broadened in the only type-II system, which means that F was also increased because it is proportional to the period of the Franz-Keldysh oscillation while the period of the Franz-Keldysh oscillations stayed unchanged in type-I system. This phenomenon is explained by that the F was affected by the band bending effect caused by the spatially separated photo-excited carriers in the interface between GaAsSb and GaAs. The F changed linearly as a function of square root of excitation power as expected for the F. Moreover, F was calculated using fast Fourier transform method for a qualitative analysis, which is in a good agreement with the theory of triangular well approximation.
11
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Zinc Oxide/Cuprous(I) Oxide-Based Solar Cells Prepared by Electrodeposition

80%
Pławecki M., Rówiński E., Mieszczak Ł.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1144-1146
EN
The aim of this research was to fabricate zinc oxide/cuprous(I) oxide-based heterojunction solar cells with the use of electrodeposition methods, and further to investigate their structures and photovoltaic properties. The ZnO and Cu₂O were used as n- and p-type semiconductors, respectively, to fabricate photovoltaic devices based on Ag/ZnO/Cu₂O/Cu(100) heterojunction structures. The crystallite sizes of ZnO and Cu₂O were determined to be 25.4(3) nm and 69.8(6) nm, respectively. It was pointed out that efficiencies of the solar cells can be gradually adjusted, using different thicknesses of Cu₂O layers, to achieve values as high as 2.7%. The standard diode model and high device performance provide new insights into the issue, outlining guidelines for high-performance solar cells and suggesting that a metal-n-type semiconductor-p-type semiconductor nanostructure-crystal layered, sandwiched-type architecture is a promising platform: to boost the efficiency.
12
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Structural and Electrical Properties of Electrodeposited Single Junction of Cuprous (I) Oxide-Copper

80%
Rówiński E., Pławecki M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1141-1143
EN
Cuprous (I) oxide (Cu₂O)-based solar cells were fabricated with the use of the electrodeposition technique at nanometre-scale, and the structural, morphological and electrical properties were investigated. The Cu₂O layers were electrodeposited on crystalline and polycrystalline copper substrates. To complete the Cu₂O/Cu(100) and Cu₂O/Cu interfaces as the solar cells the top electrodes of silver paste were painted on the rear of Cu₂O. The microscopic analysis exhibits uneven surface morphologies of a Cu₂O film with the roughness of 92.5 nm, while the X-ray diffraction analysis reveals that the layers are Cu₂O-type polycrystalline structures with the thickness of 493 nm and the crystallite size of 69.8(6) nm. The theoretical analysis of the current-voltage curve was provided to determine the values of electrical parameters of the most efficient solar cell of Ag/Cu₂O/Cu(100) and clearly indicate presence of two Schottky barriers at interfaces.
13
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Optical Transitions between Confined and Unconfined States in p-Type Asymmetric GaAs/InGaAs/AlGaAs QW Structures

80%
Sitarek P., Ryczko K., Misiewicz J., Reuter D., Wieck A.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 5
849-851
EN
We present contactless surface photovoltage spectroscopy and photoreflectance studies of 10 nm wide, p-type doped asymmetric GaAs/InGaAs/AlGaAs quantum well structures. The MBE grown structures differ in spacer thickness between the quantum well and the reservoir of holes. The doping causes that quantum well is placed in electric field. The surface photovoltage spectroscopy measurements gave us detailed information about the optical transitions between confined states and between confined and unconfined states. The comparison of experimental and numerical analysis allows us to identify all features present in the surface photovoltage spectroscopy and photoreflectance spectra. It has been found that spacer layer thickness has significant influence on surface photovoltage spectroscopy spectra.
14
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SbSI Single Nanowires as Humidity Sensors

80%
Mistewicz K., Nowak M., Szperlich P., Jesionek M., Paszkiewicz R.
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vol. 126
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issue 5
1113-1114
EN
For the first time influence of humidity on photoconductivity transient characteristics are studied for antimony sulfoiodide (SbSI) single nanowires. While negative photoconductivity is observed for SbSI gel, made up of large quantity of nanowires, only the positive effect occurs for SbSI single nanowires. Photoconductivity current response on switching on and off illumination in moist N_{2} represents so-called hook anomaly.
15
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Electronic Properties of InAs/GaAs Self-Assembled Quantum Dot Structures and Devices Studied by Photocurrent Spectroscopy

80%
Mowbray D. J., Fry P. W., Skolnick M. S., Itskevich I. E., Harris L., Ashmore A. D., Finley J. J., Wilson L. R., Schumacher K. L., Barker J. A., O'Reilly E. P., Al-Khafaji M., Cullis A. G., Hopkinson M., Clark J. C., Hill G.
Acta Physica Polonica A
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2000
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vol. 98
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issue 3
279-293
EN
The power of photocurrent spectroscopy to study the electronic properties of InAs/GaAs self-assembled quantum dots is described. From comparison of results from different samples it is shown that photocurrent provides a direct means to measure absorption spectra of quantum dots. Studies in high electric field enable the electron-hole vertical alignment to be determined. Most surprisingly this is found to be opposite to that predicted by all recent predictions. Comparison with theory shows that this can only be explained if the dots contain significant amounts of gallium, and have a severely truncated shape. The nature of the ground and excited state transitions, carrier escape mechanisms from dots, in-plane wave function anisotropies and the modal gain of a quantum dot laser are determined.
16
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Modeling of Transient Photocurrent in Organic Semiconductors Incorporating the Annihilation of Excitons on Charge Carriers

80%
Głowienka D., Szmytkowski J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
397-400
EN
The role of the annihilation of excitons on charge carriers has been theoretically investigated in organic semiconductors. We have developed the numerical drift-diffusion model by incorporation terms which describe the annihilation process. The transient photocurrent has been calculated for different injection barrier heights, exciton mobilities, and annihilation rate constants. We have demonstrated that the annihilation has a great influence on the range and the rising time of the photocurrent.
17
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Characteristics of Optical and Photoconductive Properties in Bulk and Thin Film of TlS_2 Single Crystals

70%
Badr A.
Acta Physica Polonica A
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2007
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vol. 112
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issue 1
77-91
EN
The photoconductivity measurements were carried out for bulk single crystals of TlS_2 by using the steady state (dc) method in order to elucidate the nature of the dc photoconductivity in these crystals. The photoconductivity measurements were carried out in the temperature range of 77-300 K, excitation intensity range of 2150-5050 lx, applied voltage range of 10-25 V, and wavelength range of 400-915 nm. As a result of the dc photoconductivity, the temperature dependence of the energy gap width was described and the temperature coefficient of the band gap was determined. Reflectance and transmittance spectra of the TlS_2 thin films were measured in the incident photon energy range of 2.1-2.45 eV and in the temperature range of 77-300 K. With the aid of these spectra, the temperature dependence of optical transports and parameters were elucidated. In the low energy region of the studied incident photon energy range, the above-mentioned spectra were analyzed for describing the refractive index as a function of wavelength. As results of the refractive index-wavelength variations, both the oscillator and dispersion energies of the refractive index were thereafter estimated.
18
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Effect of Spectral Irradiance Distribution on the Performance of Solar Cells

70%
Guechi A., Chegaar M., Merabet A.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-43-A-46
EN
In this paper, the global and diffuse solar radiation incident on solar cells is simulated using a spectral model SMARTS2, for varying atmospheric conditions on the site of Setif. The effect of changes in total intensity and spectral distribution on the short circuit current and efficiency of different kinds of thin film solar cells (CdTe, nc-Si:H and copper indium gallium selenide, CIGS) is examined. The results show a reduction in the short circuit current due to increasing turbidity. It is 18.82%, 27.06% and 26.80% under global radiation and for CdTe, nanocrystalline silicon (nc-Si:H), and CIGS solar cells, respectively. However it increases under diffuse radiation. Increasing water vapor in the atmosphere leads to a reduction in the short circuit current of 3.15%, 2.38%, and 2.45%, respectively, for CdTe, nc-Si:H, and CIGS cells under global radiation and it is not influenced under diffuse radiation. The performance of the solar cells is notably reduced, both in terms of efficiency and open circuit voltage, with increasing air mass.
19
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Measuring the Energy Landscape in Single Semiconductor Nanowires

51%
Smith L., Jackson H., Yarrison-Rice J., Jagadish C.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
316-320
EN
With the ability to design and control the physical structure of nanostructures to tune their electronic properties, it is increasingly important to measure the electronic structure of single nanostructures. Here we describe a number of experimental techniques for measuring the electronic structure of single semiconductor nanowires. The advantages, disadvantages and limitations of these methods will be described.
20
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Mott-Schottky Analysis of the P3HT:ZnS_{cubic} and P3HT:ZnS_{hexa} Bulk Heterojunction Solar Cells

51%
Abdul Kareem T.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
409-413
EN
Bulk heterojunction solar cells of sphalerite and wurtzite ZnS incorporated P3HT were fabricated and their Mott-Schottky analysis was performed to find the conduction mechanism of the devices. The analysis shows the formation of a Schottky junction and band unpinning at the P3HT:ZnS-Al contact and it confirms the hole conductivity in the active material.
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