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1
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Examples of Microstructure-Related Properties of Gallium Nitride

100%
Leszczyński M.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 4
653-661
EN
The work provides a brief overview and the latest experimental results concerning the microstructure of gallium nitride. Because of the importance for the optoelectronic and electronic technologies, mainly problems related to the lattice mismatch between substrates and GaN layers are discussed. Three main substrates, sapphire, silicon carbide and high-pressure-grown bulk GaN crystals, are compared. Mosaicity, thermal strains and surface roughnesses of the GaN layers grown on those substrates are reported. The application of high-pressure technologies makes it possible to use temperatures higher by a few hundred degrees with respect to the atmospheric pressure for which the decomposition of gallium nitride occurs at temperatures below 1000°C. Annealing at pressures higher than 10 kbar and temperatures up to 1550° C causes modifications of the microstructure of GaN heteroepitaxial layers on sapphire. For example, their mosaicity decreases as observed by narrowing of the X-ray diffraction peaks. The implanted layers recover upon high-pressure annealing and give a strong dopant-related luminescence.
2
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Anisotropic Lattice Misfit Relaxation in AlGaAs Semi-Bulk Layers Grown on GaAs Substrates by Liquid Phase Electroepitaxy

45%
Żytkiewicz Z. R., Domagała J., Bąk-Misiuk J., Dobosz D., Leszczyński M.
Acta Physica Polonica A
|
1997
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vol. 92
|
issue 5
1092-1096
EN
Experimental evidence for unidirectional microcracking in semi-bulk AlGaAs layers grown on (001) GaAs substrates is presented. The asymmetrical microcracking leads to anisotropic lattice misfit relaxation in the AlGaAs/GaAs structure and is explained in terms of higher mobility of [-110]-oriented α-type dislocations than that of β-type dislocations oriented in [110] direction.
3
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Lattice Constant of Doped Semiconductor

45%
Leszczyński M., Litwin-Staszewska E., Suski T., Bąk-Misiuk J., Domagała J.
Acta Physica Polonica A
|
1995
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vol. 88
|
issue 5
837-840
EN
The paper shows an influence of doping on lattice constant of a semiconductor. Three effects are discussed: (i) "size" effect caused by a different ionic radii of dopant and host atoms, (ii) lattice expansion by free electrons proportionally to the deformation potential of the conduction-band minimum occupied by this charge, (iii) different thermal expansion of the undoped and doped samples. The experiments have been performed by using the high resolution X-ray diffraction at 77-770 K on AlGaAs:Te and GaAs:Si.
4
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The Application of High Pressure in Physics and Technology of III-V Nitrides

39%
Grzegory I., Leszczyński M., Krukowski S., Perlin P., Suski T., Porowski S.
Acta Physica Polonica A
|
2001
|
vol. 100
|
issue Supplement
57-109
EN
Due to high bonding energy of N_2 molecule, the III-V semiconducting nitrides, especially GaN and InN require high N_2 pressure to be stable at high temperatures necessary for growth of high quality single crystals. Physical properties of GaN-Ga(l)-N_2 system are discussed in the paper. On the basis of the experimental equilibrium p-T-x data and the quantum-mechanical modeling of interaction of N_2 molecule with liquid Ga surface, the conditions for crystallization of GaN were established. The crystals obtained under high pressure are of the best structural quality, having dislocation density as low as 10-100 cm^{-2} which is several orders of magnitude better than in any other crystals of GaN. The method allows to grow both n-type substrate crystals for optoelectronics and highly resistive crystals for electronic applications. The physical properties of the pressure grown GaN measured to characterize both point defects and extended defects in the crystal lattice are discussed in the paper. A special attention is paid to the application of high pressure to reveal the nature of the point defects in the crystals and electric fields in GaN-based quantum structures. Due to their very high structural quality, the pressure grown crystals are excellent substrates for epitaxial growth of quantum structures. It opens new possibilities for optoelectronic devices, especially short wavelength high power lasers and efficient UV light emitting diodes. This is due to the strong reduction in dislocation densities in relation to existing structures (10^6-10^8 cm^{-2}) which are grown on strongly mismatched sapphire and SiC substrates. The experimental results on the epitaxial growth and physical properties of GaN-based device structures supporting above conclusions are discussed in the paper. The current development of blue laser technology in High Pressure Research Center is shortly reviewed.
5
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Crystallographic Properties of Bulk GaN Crystals Grown at High Pressure

39%
Leszczyński M., Grzegory I., Bockowski M., Jun J., Porowski S., Jasiński J., Baranowski J. M.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 4
799-802
EN
Gallium nitride bulk crystals grown at about 15 kbar and 1500 K have been examined by using the high resolution X-ray diffractometry. An anal­ysis of a set of the rocking curves of various Bragg reflections enabled us to estimate a dislocation density. For the crystals of dimensions lower than about 1 mm it is lower than 10^{-5} cm^{-2}. For bigger samples the crystallo­graphic quality worsens. With an application of the reciprocal lattice map­ping we could distinguish between internal strains and mosaicity which are both present in these crystals The results for the bulk crystals are compared with those for epitaxial layers.
6
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Impact of Thin LT-GaN Cap Layers on the Structural and Compositional Quality of MOVPE Grown InGaN Quantum Wells Investigated by TEM

39%
Ivaldi F., Kret S., Szczepańska A., Czernecki R., Kryśko M., Grzanka S., Leszczyński M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
660-662
EN
Two samples containing InGaN quantum wells have been grown by metal-organic vapor phase epitaxy on high pressure grown monocrystalline GaN (0001). Different growth temperatures have been used to grow the wells and the barriers. In one of the samples, a low temperature GaN layer (730°C) has been grown on every quantum well before rising the temperature to standard values (900°C). The samples have been investigated by transmission electron microscopy and X-ray diffraction. Photoluminescence spectra have been measured as well. The influence of the LT-GaN has been investigated in regard to its influence on the structural and compositional quality of the sample.
7
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Transformation of AlGaAs/GaAs Interface under Hydrostatic Pressure

39%
Bąk-Misiuk J., Domagała J., Trela J., Leszczyński M., Misiuk A., Hartwig J., Prieur E.
Acta Physica Polonica A
|
1996
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vol. 89
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issue 3
405-409
EN
AlGaAs layers grown by molecular beam epitaxy on GaAs substrates were investigated before and after high hydrostatic pressure (1.2 GPa) at high temperature (770 K) treatment (HP-HT treatment). An influence of HP-HT treatment on the properties of the AlGaAs/GaAs system was studied by lattice parameter measurements using the high resolution diffractometer and by X-ray topography. Observed changes in the lattice parameter of the AlGaAs layers after HP-HT treatment are related to the strain relaxation and explained by the creation of misfit dislocations and other extended defects which are visible on the topographs.
8
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Physical Properties of AlGaAs Epilayers Subjected to High Pressure - High Temperature Treatment

39%
Szuszkiewicz W., Gębicki W., Bąk-Misiuk J., Domagała J., Leszczyński M., Hartwig J.
Acta Physica Polonica A
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1997
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vol. 91
|
issue 5
1003-1007
EN
AlGaAs layers grown by molecular beam epitaxy on GaAs substrates were investigated before and after high hydrostatic pressure (1.2 GPa) at high temperature (770 K) treatment. In order to study the influence of high pressure - high temperature treatment on the physical properties of the AlGaAs layers, X-ray, electron transport and Raman scattering measurements were performed at room temperature. The observed changes in the lattice parameter, Raman spectra and free-carrier concentration were related to the strain relaxation and explained by the creation of misfit dislocations and other extended defects which were visible on the synchrotron X-ray topographs after high pressure - high temperature treatment.
9
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High Pressure Freeze-out of Electrons in Undoped GaN Crystal. Proof of Existence of Resonant Donor State (Nitrogen Vacancy)

39%
Perlin P., Teisseyre H., Suski T., Leszczyński M., Grzegory I., Jun J., Porowski S.
|
EN
We investigated free carriers related optical absorption in GaN in hy­drostatic pressures up to 30 GPa. The disappearance of this absorption at pressures close to 18 GPa was explained by trapping electrons resulting from the shift of nitrogen vacancy related donor level into the GaN energy gap at high pressure. We estimated the energetic position of this level at atmo­spheric pressure to be about 0.8 eV above the conduction band minimum.
10
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Luminescence in Highly Excited InGaN/GaN Multiple Quantum Wells Grown on GaN and Sapphire Substrates

33%
Miasojedovas S., Juršėnas S., Kurilčik G., Žukauskas A., Ivanov V., Godlewski M., Leszczyński M., Perlin P., Suski T.
Acta Physica Polonica A
|
2004
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vol. 106
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issue 2
273-279
EN
We report on high-excitation luminescence spectroscopy in In_xGa_{1-x}N/GaN multiple quantum wells grown by MOCVD over sapphire and bulk GaN substrates. High excitation conditions enabled us to achieve a screening of the built-in field by free carriers. This allowed for the evaluation of the influence of band potential fluctuations due to the variation in In-content on efficiency of spontaneous and stimulated emission. InGaN/GaN multiple quantum wells grown on bulk GaN substrate exhibit a significantly lower stimulated emission threshold and thus enhanced lateral emission. Transient and dynamic properties of luminescence indicate a significant reduction in compositional disorder in homoepitaxially grown structures
11
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Epitaxial Layers Versus Bulk Single Crystals of GaN. Temperature Studies of Lattice Parameters and Energy Gap

33%
Teisseyre H., Perlin P., Leszczyński M., Suski T., Dmowski L., Grzegory I., Porowski S., Jun J., Moustakas T.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
403-406
EN
Gallium nitride epitaxial layer grown by molecular beam epitaxy and bulk crystal grown at high pressure were examined by using X-ray diffrac­tion methods, and by optical absorption at a wide temperature range. The free electron concentration was 6 × 10^{17} cm^{-3} for the layer and about 5 × 10^{19} cm^{-3} for the bulk crystal. The experiments revealed a different po­sition of the absorption edge and its temperature dependence for these two kinds of samples. The structural examinations proved a significantly higher crystallographic quality of the bulk sample. However, the lattice constants of the samples were nearly the same. This indicated that a rather different electron concentration was responsible for the different optical properties via Burstein-Moss effect.
12
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Cubic MnTe - Growth by Molecular Beam Epitaxy and Basic Structural Characterization

33%
Zakrzewski A., Janik E., Dynowska E., Leszczyński M., Kutrowski M., Wojtowicz T., Karczewski G., Bąk-Misiuk J., Domagała J., Kossut J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
433-436
EN
We report on growth by molecular beam epitaxy of thick layers of MnTe with zinc blende structure. Films as thick as 5.6 µm were obtained. Char­acterization by X-ray diffraction proved their good structural quality. We determined the lattice constant and its temperature dependence. Broad lu­minescence due to internal Mn^{2+}- transitions was observed. It showed an unexpected temperature dependence.
13
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Effect of Doping on Ga_{1-x}Al_{x}As Structural Properties

33%
Bąk-Misiuk J., Domagała J., Paszkowicz W., Trela J., Żytkiewicz Z. R., Leszczyński M., Regiński K., Muszalski J., Härtwig J., Ohler M.
|
EN
The microstructure of Ga_{1-x}Al_{x}As layers was studied using methods of high resolution diffractometry and topography. Mapping out the reciprocal space in the vicinity of 004 reciprocal lattice points shows a difference in diffuse scattering between doped and undoped layers. This result is attributed to a difference in a point-defect density. From the measurements of lattice parameters at different temperature it was found that the thermal expansion coefficients for the doped layers are higher than for the undoped ones. This phenomenon is attributed to the change of the anharmonic part of lattice vibrations by free electrons or/and point defects.
14
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Content available

Light Emission Properties of GaN-Based Laser Diode Structures

33%
Godlewski M., Phillips M., Czernecki R., Targowski G., Perlin P., Leszczyński M., Figge S., Hommel D.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 4
675-680
EN
Cathodoluminescence is applied for evaluation of in-depth and in-plane variations of light emission from two types of GaN-based laser diode structures. We evaluate in-depth properties of the laser diode emission and demonstrate that potential fluctuations still affect emission of laser diodes for e-beam currents above thresholds for a stimulated emission.
15
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High Power Continuous Wave Blue InAlGaN Laser Diodes Made by Plasma Assisted MBE

27%
Skierbiszewski C., Siekacz M., Wiśniewski P., Perlin P., Feduniewicz-Żmuda A., Cywiński G., Smalc J., Grzanka S., Grzegory I., Leszczyński M., Porowski S.
Acta Physica Polonica A
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2006
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vol. 110
|
issue 3
345-351
EN
Room temperature, continuous wave operation of InGaN multi-quantum wells laser diodes made by rf plasma assisted molecular beam epitaxy at 411 nm wavelength is demonstrated. The threshold current density and voltage were 4.2 kA/cm^2 and 5.3 V, respectively. High optical power output of 60 mW was achieved. The lifetime of these laser diodes exceeds 5 h with 2 mW of optical output power. The laser diodes are fabricated on low dislocation density bulk GaN substrates, at growth conditions which resembles liquid phase epitaxy. We demonstrate that relatively low growth temperatures (600-700°C) pose no intrinsic limitations for fabrication of nitride optoelectronic components by plasma assisted molecular beam epitaxy.
16
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High Resistivity GaN Single Crystalline Substrates

27%
Porowski S., Boćkowski M., Łucznik B., Grzegory I., Wróblewski M., Teisseyre H., Leszczyński M., Litwin-Staszewska E., Suski T., Trautman P., Pakuła K., Baranowski J.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
958-962
EN
High resistivity 10^{4}-10^{6} Ω cm (300 K) GaN single crystals were obtained by solution growth under high N_{2} pressure from melted Ga with 0.1-0.5at.% of Mg. Properties of these crystals are compared with properties of conductive crystals grown by a similar method from pure Ga melt. In particular, it is shown that Mg-doped GaN crystals have better structural quality in terms of FWHM of X-ray rocking curve and low angle boundaries. Temperature dependence of electrical resistivity suggests hopping mechanism of conductivity. It is also shown that strain free GaN homoepitaxial layers can be grown on the Mg-doped GaN substrates.
17
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Stimulated Emission from the MBE Grown Homoepitaxial InGaN Based Multiple Quantum Wells Structures

27%
Ivanov V., Godlewski M., Miasojedovas S., Juršėnas S., Kazlauskas K., Žukauskas A., Skierbiszewski C., Siekacz M., Leszczyński M., Perlin P., Suski T., Grzegory I.
Acta Physica Polonica A
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2005
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vol. 107
|
issue 2
225-229
EN
We report on photoluminescence characterization of InGaN based laser structures grown by homoepitaxial radio frequency plasma-assisted molecular beam epitaxy. Owing to Si doped barriers, the structures show a negligible impact of the built-in electric field, which was proved by excitation intensity dependent and quantum well width dependent luminescence experiments. Relatively low variation in band potential due to inhomogeneous distribution of In was quantitatively estimated from the photoluminescence temperature behavior using Monte Carlo simulation of in-plane carrier hopping and optically detected cyclotron resonance experiments. Efficient stimulated emission with a low threshold for optically pumped laser structures was observed.
18
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Thermal Expansion of GaN Bulk Crystals and Homoepitaxial Layers

27%
Leszczyński M., Teisseyre H., Suski T., Grzegory I., Boćkowski M., Jun J., Pałosz B., Porowski S., Pakuła K., Baranowski J., Barski A.
Acta Physica Polonica A
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1996
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vol. 90
|
issue 5
887-890
EN
Thermal expansion of gallium nitride was measured using high resolution X-ray diffraction. The following samples were examined: (i) single monocrystals grown at pressure of about 15 kbar, (ii) homoepitaxial layers. The main factor influencing both, the lattice parameters and the thermal expansion coefficient, are free electrons related to the nitrogen vacancies. The origin of an increase in the lattice constants by free electrons is discussed in terms of the deformation potential of the conduction-band minimum. An increase of the thermal expansion by free electrons is explained by a decrease of elastic constants.
19
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Polarity Related Problems in Growth of GaN Homoepitaxial Layers

27%
Leszczyński M., Prystawko P., Śliwinski A., Suski T., Litwin-Staszewska E., Porowski S., Paszkiewicz R., Tłaczała M., Beaumont B., Gibart P., Barski A., Langer R., Knap W., Frayssinet E.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
427-430
EN
Homoepitaxial layers of GaN were grown by metalorganic chemical vapour deposition on single crystals obtained by high-pressure, high-temperature technology. For each metalorganic chemical vapour deposition run, four samples were placed, (00.1) and (00.1̲) faces of the Mg-doped insulating and undoped highly-conductive substrates. The layers were examined using X-ray diffraction, photoluminescence and far-infrared reflectivity. It was found that the (00.1̲) easier incorporates donors resulting in higher free-electron concentrations in the layers grown on these sides of the crystals, both, undoped and Mg-doped.
20
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Blue Laser on High N_2 Pressure-Grown Bulk GaN

21%
Grzegory I., Boćkowski M., Krukowski S., Łucznik B., Wróblewski M., Weyher J., Leszczyński M., Prystawko P., Czernecki R., Lehnert J., Nowak G., Perlin P., Teisseyre H., Purgał W., Krupczyński W., Suski T., Dmowski L., Litwin-Staszewska E., Skierbiszewski C., Łepkowski S., Porowski S.
Acta Physica Polonica A
|
2001
|
vol. 100
|
issue Supplement
229-232
EN
In this note we report briefly on the details of pulsed-current operated "blue" laser diode, constructed in our laboratories, which utilizes bulk GaN substrate. As described in Ref. [1] the substrate GaN crystal was grown by HNPSG method, and the laser structure was deposited on the conducting substrate by MOCVD techniques (for the details see Sec. 2 and Sec. 4 of Ref.~[1], respectively).
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