Wyniki wyszukiwania - Biblioteka Nauki

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Deep levels in GaN studied by deep level transient spectroscopy and Laplace transform deep-level spectroscopy

100%

Kamyczek P. , Placzek-Popko E. , Zielony E. , Zytkiewicz Z.

Materials Science Poland

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2013

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tom Vol. 31, No. 4

572--576

EN

In this study we present the results of investigations on Schottky Au–GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77 – 350 K. Si-doped GaN layers were grown by Molecular Beam Epitaxy technique (MBE) on sapphire substrates. DLTS signal spectra revealed the presence of four majority traps: two hightemperature and two low-temperature peaks. Using LDLTS method and Arrhenius plots the activation energy and capture cross sections were obtained. For two high-temperature majority traps they are equal to E1 = 0.65 eV, s1 = 8.2 × 10<-16/sup>cm2 and E2 = 0.58 eV, s2 = 2.6 × 10<-15/sup> cm2 whereas for the two low-temperature majority traps E3 = 0.18 eV, s3 = 9.72 × 10<-18/sup> cm2 and E4 = 0.13 eV, s4 = 9.17 × 10<-18/sup> cm2. It was also found that the traps are related to point defects. Possible origin of the traps was discussed and the results were compared with the data found elsewhere [1–5].

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Raman spectroscopy of CdTe/ZnTe quantum dot structures

88%

Zielony E. , Placzek-Popko E. , Kamyczek P. , Henrykowski A. , Karczewski G.

Optica Applicata

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2013

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tom Vol. 43, nr 1

181--185

EN

Semiconductor low-dimensional structures of CdTe quantum dots (QDs) embedded in ZnTe matrix have been investigated by micro-Raman spectroscopy. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by a molecular beam epitaxy technique on the p-type GaAs substrate. The Raman measurements have been performed at room temperature. The samples were excited by an Ar2+ laser of 514.5 nm wavelength. The Raman spectra have been recorded for different acquisition parameters of the measurement. For the reference and QD sample localized longitudinal (LO) phonons of 210 cm–1 wavenumber associated with the ZnTe layer are observed. In the case of QD sample another broadband corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm–1. Such behaviour does not exhibit the Raman spectra of the reference sample. Thus the Raman measurements confirm the presence of CdTe layer of quantum dots in the investigated material. Additionally, Raman spectra for both samples exhibit tellurium-related peaks at wavenumbers around 120 cm–1 and 140 cm–1, significantly increasing with laser time exposure. It is shown that the peaks are associated with the formation of Te aggregates on the ZnTe surface due to the laser damage in the ZnTe layer.

3

GaAsN as a photovoltaic material : photoelectrical characterization

75%

Kamyczek P. , Płaczek-Popko E. , Biegański P. , Zielony E. , Ściana B. , Tłaczała M.

Elektronika : konstrukcje, technologie, zastosowania

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2012

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tom Vol. 53, nr 6

109-110

EN

In summary, we present in this study the results of studies on the layers of GaAs1-xNx grown on n-type GaAs substrates by atmospheric pressure metal organic vapour phase epitaxy (APMOVPE), Using transmittance, reflectance, photocurrent measurements and empirical expression for Eg a new nitrogen content for the studies samples was obtained. Using dark and illuminated I-V characteristics the main parameters of the Schottky contacts (short-circuit current Isc, open circuit-voltage, Voc, and fill factor, FF) were determined. Obtained contacts are promising for solar cell application.

4

Photoelectrical properties of photovoltaic structures based on CdTe/ZnO

75%

Zielony E. , Kamyczek P. , Biegański P. , Płaczek-Popko E. , Pietruszka R. , Łuka G. , Godlewski M.

Elektronika : konstrukcje, technologie, zastosowania

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2012

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tom Vol. 53, nr 6

100-101

EN

The n-type ZnO layers were grown by ALD method on p-type CdTe substrate. I-V characteristics verified rectifying properties of the test ZnO/CdTe solar cell diode and exhibited photovoltaic effect when the junction was exposed to light. The series resistance of the diode, determined from the I-V curves, equals to 36 Ω. Such a high value is responsible for low value of fill factor and efficiency of the solar cell. Photoresponse properties of the studied junction were measured at room temperature. Efficient photoresponse was observed within wavelength range of 400-1000 nm. These results indicate that n-ZnO/p-CdTe junction is suitable for the fabrication of efficient solar cells. It was shown that the thickness of the ZnO layers can be also determined with the help of interference fringes of photoresponse analysis. Further work will involve a better understanding of the properties of window layer and junction formation processes.

5

Electro-optical properties of diluted GaAsN on GaAs grown by APMOVPE

51%

Kamyczek P. , Biegański P. , Płaczek-Popko E. , Zielony E. , Gelczuk Ł. , Sciana B. , Pucicki D. , Radziewicz D. , Tlaczala M. , Kopalko K. , Dabrowska-Szata M.

Materials Science Poland

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2013

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tom Vol. 31, No. 4

595--600

EN

In this paper we report on the optical and electrical studies of single GaAs1-xNx epitaxial layers grown on GaAs substrates by means of atmospheric pressure metal organic vapour phase epitaxy (APMOVPE). Three kinds of samples with 1.2 %, 1.6 % and 2.7 % nitrogen content were studied. Optical properties of the layers were investigated with the use of room temperature transmittance and reflectance measurements. Subsequently Schottky Au–GaAs1-xNx contacts were processed and characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements within 80 – 480 K temperature range. From the I-V and C-V characteristics the ideality factor, series resistance and built-in potential were determined. Obtained diodes can be used for further studies on defects with the use of DLTS method.