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  1. 27 Acta Physica Polonica A

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  1. 27 Suski T.

  2. 12 Grzegory I.

  3. 12 Perlin P.

  4. 10 Leszczyński M.

  5. 10 Porowski S.

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1
Content available remote

DX Puzzle: Where Are We Now?

100%
Wilamowski Z., Suski T., Jantsch W.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 4
561-571
EN
A brief review of the experimental data on the metastable DX-centers in AlGaAs is presented. The experimental proofs of the two-electron nature and of the intermediate, one-electron state of the DX-centers are discussed. We collect the available experimental data on the ground state, electron-emission and capture energies and we discuss the nature of the lattice barrier. The effect of splitting of these energies in AlGaAs alloys and the consequences of the splitting on the capture and emission kinetics are analyzed. The different character of the barrier and of the alloy splitting for donors of the IV and VI group is underlined. The necessity to consider the interdonor Coulomb interaction when discussing the experimental data is also pointed out.
2
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Metastability of Localized Neutral Donor State In GaAs

88%
Skierbiszewski C., Jantsch W., Lübke K., Wilamowski Z., Suski T.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 5
905-908
EN
Investigations of the photoconductivity of GaAs:Ge under hydrostatic pressure show, in addition to the well known persistent photoconductivity due to the DX state, another giant photoconductivity caused by a neutral localised "A₁" state of the donor. We find that the top of the barrier for the electron recapture to the Α₁ state is pinned to the conduction band edge and the capture cross-section σ(T → ∞) is surprisingly small.
3
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Electron Scattering and the Band Structure of Mixed Crystals Hg_{1-x}Fe_{x}Se

88%
Skierbiszewski C., Wilamowski Z., Suski T., Kossut J., Witkowska B.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
809-812
EN
In this paper the dependence of the band structure and the electron scattering mechanisms on the molar fraction x are studied in Hg_{1-x}Fe_{x}Se. The crossover from the zero-gap band to the open band-gap configuration at x ≈ 0.08 is predicted. We explain the drop of the electron mobility for x > 0.002 by the alloy scattering mechanism.
4
Content available remote

Lattice Constant of Doped Semiconductor

88%
Leszczyński M., Litwin-Staszewska E., Suski T., Bąk-Misiuk J., Domagała J.
Acta Physica Polonica A
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1995
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vol. 88
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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.
5
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The Application of High Pressure in Physics and Technology of III-V Nitrides

76%
Grzegory I., Leszczyński M., Krukowski S., Perlin P., Suski T., Porowski S.
Acta Physica Polonica A
|
2001
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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.
6
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A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

76%
Dróżdż P., Korona K., Sarzyński M., Czernecki R., Skierbiszewski C., Muzioł G., Suski T.
Acta Physica Polonica A
|
2016
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vol. 130
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issue 5
1209-1212
EN
The potential fluctuations in III-nitride quantum wells lead to many effects like emission broadening and S-shape energy vs. temperature dependence. The best description of the energy dependence comes from calculations based on Gaussian density of states. However, in most of the published reports, changes of carrier lifetime with energy and temperature are not taken into account. Since experimental evidence shows that lifetime significantly depends on energy and temperature, here we propose a model that describes two basic parameters of luminescence: lifetime of carries and emission energy as a function of temperature in the case of quantum wells and layers that are characterized by potential fluctuations. Comparison of the measured energy and lifetime dependences on temperature in specially grown InGaN/GaN quantum wells and InAlGaN layer shows very good agreement with the proposed theoretical approach.
7
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Pressure Study of Charged Donor Ordering in HgSe Doped with Iron and Gallium

76%
Skierbiszewski C., Suski T., Kossut J., Wilamowski Z., Dobrowolski W., Witkowska B.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 3
401-404
EN
Transport experiments (Hall effect and conductivity) under hydrostatic pressure up to 1 GPa at liquid helium temperatures on HgSe: Fe, Ga (N_{Fe} = 2 x 10^{19} cm^{-3}; 0 ≤ N_{Ga} ≤ 10^{19} cm^{-3}) were performed. The results show that the gallium co-doping of HgSe:Fe decreases the degree of spatial correlations between charged impurities. Under the hydrostatic pressure, used as a tool for changing the ratio of the charged to neutral impurities, this effect is even more pronounced. A qualitative agreement between the calculation within the short-range correlation model and our experimental data is achieved.
8
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Band Structure and Refractive Index of Gallium Nitride Under Pressure

76%
Perlin P., Gorczyca I., Suski T., Teisseyre H., Grzegory I., Christensen N.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
421-424
EN
The effect of hydrostatic pressure on direct gap and refractive index of GaN is investigated up to 5.5 GPa. Band structure of GaN is calculated by Linear Muffin-Tin Orbitals (LMTO) method for different values of pressure. Resulting pressure coefficient of the main gap and of the refractive index are in a good agreement with the experimental ones.
9
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Interplay between Internal and External Electric Field Studied by Photoluminescence in InGaN/GaN Light Emitting Diodes

76%
Staszczak G., Khachapuridze A., Grzanka S., Czernecki R., Piotrzkowski R., Perlin P., Suski T.
Acta Physica Polonica A
|
2011
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vol. 120
|
issue 5
891-893
EN
We have studied a series of polar InGaN/GaN light emitting diodes, consisting of either a blue (440-450 nm) quantum well, or combination of blue and violet (410 nm) quantum wells (with indium content 18% and 10%, respectively). The blue quantum well was always placed close to p-type region of the particular LED. We found that the electroluminescence induced by low current is characterized by light emission from the blue quantum well only. In comparison, optical excitation of our LEDs leads to light emission with energies characteristic either for blue and/or violet quantum wells. The corresponding microphotoluminescence spectra evolve depending on external polarization and variable light intensity of excitation supplied by He-Cd laser. Interplay between built-in electric field and externally applied polarization/screening decides about the band structure profiles and thus radiative recombination mechanisms.
10
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Deep Levels in GaN p-n Junctions Studied by Deep Level Transient Spectroscopy and Laplace Transform Deep-Level Spectroscopy

76%
Dyba P., Placzek-Popko E., Zielony E., Gumienny Z., Grzanka S., Czernecki R., Suski T.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 5
669-671
EN
p^+-n GaN diodes were studied by means of conventional deep level transient spectroscopy and Laplace transform deep-level spectroscopy methods within the temperature range of 77-350 K. Deep level transient signal spectra revealed the presence of a majority and minority trap of indistinguishable signatures. The Laplace transform deep-level spectroscopy technique due to its superior resolution allows us to unambiguously identify and characterize the traps. The apparent activation energy and capture cross-section for the majority trap were found to be equal to 0.63 eV and 2 × 10^{-16} cm^2 and for the minority trap 0.66 eV and 1.6 × 10^{-15} cm^2. It has been confirmed that the Laplace transform deep-level spectroscopy technique is a powerful tool in characterization of the traps of close signatures.
11
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Hydrostatic Pressure Studies of Asymmetric Double-Barrier Resonant Tunneling Diodes

76%
Diniz R., Smoliner J., Gornik E., Suski T., Meiners U., Brugger H.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 4
625-628
EN
Tunneling processes in double-barrier GaAs/AlAs diodes with an incorporated AlGaAs pre-barrier were studied under hydrostatic pressure. The electrical characteristics resulting from a pre-barrier on the side of the emitter can be explained at 1 bar, solely by the Γ-profile: increasing pressure shows that the pre-barrier does not reduce the Γ-X tunneling. A pre-barrier on the collector side leads to charge buildup at the X minimum within the AlAs collector barrier.
12
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Content available

The Role of Internal Electric Fields in III-N Quantum Structure

76%
Perlin P., Łepkowski S., Teisseyre H., Suski T., Grandjean N., Massies J.
Acta Physica Polonica A
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2001
|
vol. 100
|
issue 2
261-270
EN
Binary nitrides: of wurtzite GaN, AlN, InN, and their solid solutions represent a family of semiconductors of crucial importance for modern optoelectronics. Strained quantum wells, like GaN/AlGaN and specially InGaN/GaN, form active layers of the light emitters working in green-UV part of the spectrum. The operation of these devices strongly depends on the emission spectra of considered quantum structures which are greatly influenced by the presence of built-in electric fields. The electric field acting via quantum confined Stark effect in the mentioned structures changes the energies and intensity of the emitted light. The effect can lead to the spectral shift of a photo- and electroluminescence by many hundreds of meV. In this review we will briefly cover the influence of internal electric fields on both optical and electrical properties of nitride based heterostructures and quantum wells. We would like to draw reader's attention to the usefulness of high-pressure investigation in the study of electric fields in nitrides and to show how the interpretation of these experiments influences the way we calculate the electric fields in the quantum structures.
13
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High Pressure Freeze-out of Electrons in Undoped GaN Crystal. Proof of Existence of Resonant Donor State (Nitrogen Vacancy)

76%
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.
14
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Optical and Electrical Properties of High Temperature Annealed Heteroepitaxial GaN:Mg Layers

76%
Wojdak M., Baranowski J. M., Suchanek B., Pakuła K., Jun J., Suski T.
Acta Physica Polonica A
|
1997
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vol. 92
|
issue 5
1059-1062
EN
In this paper we present for the first time luminescence and electrical measurements of GaN:Mg heteroepitaxial layers annealed at very high temperatures up to 1500°C and at high pressures of nitrogen up to 16 kbar. The presence of high nitrogen pressure prevents GaN from thermal decomposition. It was found that annealing in the presence of additional Mg atmosphere leads to a high quality p-type epitaxial layer of the hole concentration equal to 2×10^{17} cm^{-3} and mobility 16 cm^{2}/(V s). However, annealing at high temperatures without additional magnesium causes conversion to n-type. It is also shown that in the high temperature annealed GaN:Mg epilayers the donor-acceptor luminescence is the dominant recombination channel.
15
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Spatial Correlations of Donor Charges in MBE CdTe

64%
Suski T., Wiśniewski P., Litwin-Staszewska E., Wasik D., Przybytek J., Baj M., Karczewski G., Wojtowicz T., Zakrzewski A., Kossut J.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 5
929-932
EN
We present experimental evidence that at high pressures indium donors in CdTe localize electrons in spatially correlated manner. We have studied Hall mobility, μ_{H}, as a function of electron concentration, n_{H}, at T=77 K. Changes of n_{H} have been achieved by two methods. High pressure freeze-out of electrons onto localized states of In-donors leads to the mobility enhancement with respect to the situation when n_{H} has been modified by means of a subsequent annealing of the sample. As a result, depending on the degree of spatial correlations in the impurity charges arrangement, different values of μ_{H} correspond to the same value of n_{H}. The variation of mobility with electron concentration suggests that the localized state of In-donor represents likely negatively charged DX state.
16
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Luminescence in Highly Excited InGaN/GaN Multiple Quantum Wells Grown on GaN and Sapphire Substrates

64%
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
|
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
17
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Epitaxial Layers Versus Bulk Single Crystals of GaN. Temperature Studies of Lattice Parameters and Energy Gap

64%
Teisseyre H., Perlin P., Leszczyński M., Suski T., Dmowski L., Grzegory I., Porowski S., Jun J., Moustakas T.
Acta Physica Polonica A
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1995
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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.
18
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III-V Semiconducting Nitrides Energy Gap under Pressure

64%
Perlin P., Gorczyca I., Teisseyre H., Suski T., Litwin-Staszewska E., Porowski S., Grzegory I., Christensen N.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 4
674-676
EN
In this paper we present overview of our recent experimental and theoretical results concerning electronic band structure of III-V nitrides under pressure. It is shown here that the pressure coefficients of the direct gap for studied nitrides are surprisingly small. To describe tendency in changes of the gap with pressure we use a simple empirical relation.
19
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Two-Electron DX State in CdTe:In

64%
Skierbiszewski C., Wiśniewski P., Litwin-Staszewska E., Suski T., Wilamowski Z., Zakrzewski A., Karczewski G., Jantsch W.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 5
927-930
EN
In this paper we investigate electron emission/capture from/to the DX state of indium in CdTe by means of high pressure freeze-out cycle and steady-state photo-conductivity experiments. The results indicate that the DX state is occupied by two electrons. A comparison with deep level transient spectroscopy data shows that two-electron emission occurs at low temperatures, while one-electron emission takes place at high temperatures.
20
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Mechanisms of Yellow and Red Photoluminescence in Wurtzite and Cubic GaN

64%
Godlewski M., Suski T., Grzegory I., Porowski S., Langer R., Barski A., Bergman J., Monemar B., Goldys E., Phillips M.
Acta Physica Polonica A
|
1998
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vol. 94
|
issue 2
326-330
EN
The origin of two "deep" photoluminescence (PL) emissions observed in wurtzite (yellow PL) and cubic (red PL) GaN is discussed. PL and time-resolved PL studies confirm donor-acceptor pair character of the yellow band in wurtzite GaN and point to participation of shallow donors in this emission. A similar PL mechanism is proposed for the red emission of cubic GaN. We further show a puzzling property of both yellow and red PLs. Both yellow and red emissions show spatial homogeneity and are only weakly dependent on surface morphology.
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