Wyniki wyszukiwania - Biblioteka Nauki

1

Wyznaczanie naprężeń w strukturach epitaksjalnych GaN

100%

Korbutowicz R.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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tom Vol. 50, nr 1

30-32

PL

Artykuł omawia zagadnienia związane z możliwościami jakie daje spektroskopia mikrbramanowska w analizie warstw epitaksjalnych azotku galu: wyznaczanie naprężeń i rozkładu naprężeń oraz odkształcenia w strukturach epitaksjalnych, a tym samym określenie jakości kryształu powierzchniowego. Możliwość jakościowej i ilościowej analizy wynika z faktu, że widmo Ramana jest charakterystyczne dla danego rodzaju atomów lub cząsteczek (ich drgań), zaś jego intensywność zależy od liczby rozproszonych nieelastycznie fotonów.

EN

A paper is devoted to possibility of the microRaman speetroscopy applications in area of gallium nitride epilayers analyzes, especially determination of the stress and the stress distribution as well as strains in epitaxial structures. It can give information about the surface's crystal quality. Micro-Raman spectroscopy is one of the sensitive methods for giving information about the stress in epilayers. These huge possibilities of quality and quantity estimation arise from characteristic reaction of atoms and molecules - i.e. their vibrafions and Raman spectrum intensity depends on the inelastic scattered photons quantity.

2

Preliminary comparison of three processes of AlN oxidation: dry, wet and mixed ones

63%

Korbutowicz R. , Zakrzewski A.

Materials Science Poland

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2016

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tom Vol. 34, No. 1

157--163

EN

Three methods of AlN layers oxidation: dry, wet and mixed (wet with oxygen) were compared. Some physical parameters of oxidized thin films of aluminum nitride (AlN) layers grown on silicon Si(1 1 1) were investigated by means Energy-Dispersive X-ray Spectroscopy (EDS) and Spectroscopic Ellipsometry (SE). Three series of the thermal oxidations processes were carried out at 1012 degrees C in pure nitrogen as carrying gas and various gas ambients: (a) dry oxidation with oxygen, (b) wet oxidation with water steam and (c) mixed atmosphere with various process times. All the research methods have shown that along with the rising of the oxidation time, AlN layer across the aluminum oxide nitride transforms to aluminum oxide. The mixed oxidation was a faster method than the dry or wet ones.

3

Optimization of multi quantum well solar cell

63%

Prażmowska J. , Korbutowicz R.

Optica Applicata

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2005

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tom Vol. 35, nr 3

619-626

EN

Quantum well solar cell with GaAs wells and AlxGa1-xAs barriers was optimized. Particular emphasis was placed on enhancing the efficiency. Open-circuit voltage, short-circuit current density, fill factor have been also optimized. Many simulations of various structures were carried out. The conversion efficiency exceeding 27% was obtained. The algorithm of structures optimization that gives comprehensive information about solar cells parameters in a short time was shown. Spectral characteristics, efficiency of energy conversion as a function of light concentration, temperature and the geometrical and materials parameters of the solar cells structures were determined. These results are compared with nearly identical p-i-n solar cells: i) the first with /-region made from undoped GaAs (well material) and ii) the second with /-region from A0.1Ga0.9As (barrier material).

4

Parameters comparison of p-i-n and quantum well solar cells

51%

Prażmowska J. , Korbutowicz R. , Paszkiewicz R. , Tłaczała M.

Optica Applicata

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2007

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tom Vol. 37, nr 4

371-376

EN

Double gallium arsenide quantum wells (2QW) were inserted within AlxGa1-xAs barriers of the intrinsic layer of an ordinary solar cell. Structure parameters have strong influence on device performance and should be precisely controlled in order to obtain the enhancement of conversion efficiency. Computer simulations of solar cells were carried out by SimWindows program v. 1.5.0. Some parameters of optimized quantum well solar cells (QWSC) and reference p-i-n solar cell structures, like: series resistance Rs, shunt resistance Rsh, emission coefficients (n1 and n2), diffusion and recombination components of current (Jd and Jr) were compared.

5

Photoreflectance and photoluminescence of thick GaN layers grown by HVPE

45%

Kudrawiec R. , Korbutowicz R. , Paszkiewicz R. , Syperek M. , Misiewicz J.

Opto-Electronics Review

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2004

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tom Vol. 12, No. 4

435-439

EN

Very thick (up to 100 µm) GaN layers grown by HVPE are investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopies. The layers were deposited on a GaN buffer layer which was grown on a c-plane sapphire substrate by MOVPE. Both, N- and Ga-polar layers were selected to these investigations. We have observed a strong dependence of the optical properties on the polarity of GaN surface. We have obtained that the bandgap-related emission for Ga-polar layers is stronger and narrower than the emission for N-polar layers. Also, significant differences have been found in PR spectra of the two type layers. In the case of Ga-polar layer a broad PR resonance with Franz-Keldysh oscillation (FKO) related to the surface electric field (215 kV/cm) has been observed, while in the case of N-polar layer narrow resonances have been found as being predominant. No-FKO for N-polar layer indicates that the surface electric field for this layer is weak. It means that the surface barrier for N-polar GaN is much smaller than for Ga-polar GaN layer.

6

Gallium oxide buffer layers for gallium nitride epitaxy

45%

Korbutowicz R. , Wnek J. , Panachida P. , Serafinczuk J. , Srnanek R.

Optica Applicata

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2013

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tom Vol. 43, nr 1

73--79

EN

Gallium nitride (GaN) is very attractive semiconductor material because of its unique properties. The serious matter is a lack of easy access to bulk crystals of GaN. Synthesized crystals are precious and rather small. For these reasons almost all device manufacturers and researchers apply alternative substrates for gallium nitride devices epitaxy and it causes that the technology is intricate. Alternative substrates need buffer layers – their technology is usually complex and expensive. We have proposed a simple method to avoid large costs: applying gallium oxide – monoclinic β-Ga2O3, as the buffer layer, which has structural properties quite good matched to GaN. As the substrates made from single crystal gallium oxide are still hardly available on the market, we have used hydride vapour phase epitaxy (HVPE) GaN epilayers as a starting material. It can be GaN layer under good quality – middle or low. The oxidation process converts top GaN to β-Ga2O3 layer which can release or absorb the strain. Applying such structure in another, second, epitaxy of GaN allows to obtain good quality epitaxial structures using HVPE technique.

7

Solar cells conversion efficiency enhancement techniques

45%

Prażmowska J. , Paszkiewicz R. , Korbutowicz R. , Wosko M. , Tłaczala M.

Optica Applicata

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2007

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tom Vol. 37, nr 1-2

93-99

EN

In order to enhance the conversion efficiency of GaAs p-i-n solar cells GaAs/AlxGa1-xAs QW within intrinsic region or gradation of Al fraction of AlxGa1-xAs emitter and base region were applied. The influence of AlAs Bragg reflectors on the performance of MQWSC was studied theoretically by using SimWindows software.

8

Photoreflectance spectra of MOVPE-grown InxGa1-xAs/GaAs MQW - the temperature dependence.

45%

Sęk G. , Misiewicz J. , Radziewicz D. , Korbutowicz R. , Tłaczała M.

Optica Applicata

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1999

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tom Vol. 29, nr 3

301-308

9

Photoreflectance spectroscopy of thick GaN layers grown by hydride vapour phase epitaxy technique

38%

Syperek M. , Kudrawiec R. , Misiewicz J. , Korbutowicz R. , Paszkiewicz R. , Tłaczała M.

Optica Applicata

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2005

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tom Vol. 35, nr 3

529-535

EN

The room temperature photoreflectance (PR) spectroscopy was used to investigate thick GaN epitaxial layers. The GaN layers were grown by hydride vapour phase epitaxy (HVPE) technique and compared to thin GaN layer grown by metalorganic vapour phase epitaxy (MOVPE) technique on AlN buffer layer. We observed energy red shift of the PR resonance for HVPE GaN layers compared with MOVPE GaN layer. This blue shift is due to reduction of the strain in HVPE layer. In addition, weak PR features related to Franz-Keldysh oscillations (FKO) have been observed. The electric field determined from the FKO period is 28 and 71 kV/cm for MOVPE and HVPE layers, respectively.

10

Influence of the deposition parameters of nucleation layer on the properties of thick gallium nitride layers

38%

Prażmowska J. , Korbutowicz R. , Paszkiewicz R. , Szyszka A. , Podhorodecki A. , Misiewicz J. , Tłaczała M.

Materials Science Poland

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2008

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tom Vol. 26, No. 1

79--85

EN

Gallium nitride layers were grown on sapphire (0001) substrates on low temperature (LT)-GaN layer deposited by the HVPE method. HCl flow rates and deposition times of the nucleation layer were varied in the range of 8-10 cm3/min and 5-9 min (with the step of 2 min), respectively. Morphologies of LTGaN buffer layers and subsequent high temperature (HT)-GaN layers were examined by scanning electron microscopy. Photoluminescence spectra of HT-GaN layers were recorded which allowed us to evaluate the optical quality of thick HVPE HT-GaN layers.

11

Advanced technology of AIII-BV and AIII-N structures for microelectronics application

32%

Boratyński B. , Korbutowicz R. , Paszkiewicz B. , Paszkiewicz R. , Pucicki D. , Radziewicz D. , Ściana B. , Tłaczała M.

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12

Optical studies of MOVPE grown GaN layers

32%

Ciorga M. , Jezierski K. , Bryja L. , Misiewicz J. , Paszkiewicz R. , Korbutowicz R. , Panek M. , Paszkiewicz B. , Tłaczała M. , Trabjerg I.

Opto-Electronics Review

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1999

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tom Vol. 7, No. 2

93-95

EN

Photoluminescence and reflectance studies of MOVPE grown GaN samples were performed. From reflectance measurements optical constants were calculated by means of Kramers-Kronig analysis in the energy region 0-6 eV.