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1

Application of GaN Pressure Grown Crystals for Epitaxy of GaN-Based Structures

100%

Grzegory I.

Acta Physica Polonica A

|

2000

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vol. 98

|

issue 3

183-193

EN

The results obtained with the use of the pressure grown GaN single crystalline substrates allow to draw the following conclusions important for the construction of In-free UV light emitting diodes and lasers and InGaN-based high power blue lasers: 1. The application of the pressure grown GaN single crystalline substrates allows to grow near dislocation free layer structures by both metal organic chemical vapor deposition and MBE. 2. The elimination of dislocations leads to highly efficient UV emission from GaN and GaN/AlGaN quantum wells which is impossible for strongly dislocated structures grown on sapphire. 3. At high excitations (i.e. in lasers) dislocations are effective nonradiative recombination centers also in the InGaN containing structures, therefore the elimination of these defects is crucial for better performance of blue lasers. 4. The analysis of microstructural and optical properties of the InGaN containing dislocation free structures shows that the main mechanisms of carrier localization in InGaN are not related with the nm scale compositional fluctuations in InGaN. In the paper, the optical and structural properties of the near dislocation free GaN-based structures leading to the above conclusions are discussed.

2

The Application of High Pressure in Physics and Technology of III-V Nitrides

40%

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.

3

Observation of Magnetic Anisotropy in Bulk GaMnN:Mg Crystals

40%

Gosk J., Zając M., Kamińska M., Twardowski A., Grzegory I., Boć M., Porowski S.

Acta Physica Polonica A

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2003

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vol. 103

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issue 6

665-669

EN

Magnetic properties of bulk wurtzite n-type GaMnN and highly resistive GaMnN:Mg monocrystals were studied for the magnetic field applied parallel and perpendicular to the crystal hexagonal c-axis. Magnetization of both types of samples reveals paramagnetic behavior. However, for n-type GaMnN isotropic magnetization was observed which is in agreement with Mn d^5 configuration. On the other hand, GaMnN co-doped with Mg shows large magnetic anisotropy which suggests Mn to be in nonspherical d^4 or d^3 configuration.

4

Crystallographic Properties of Bulk GaN Crystals Grown at High Pressure

40%

Leszczyński M., Grzegory I., Bockowski M., Jun J., Porowski S., Jasiński J., Baranowski J. M.

Acta Physica Polonica A

|

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.

5

Band Structure and Refractive Index of Gallium Nitride Under Pressure

40%

Perlin P., Gorczyca I., Suski T., Teisseyre H., Grzegory I., Christensen N.

Acta Physica Polonica A

|

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.

6

Deep-Level Defects in MBE-Grown GaN-Based Laser Structure

40%

Tsarova T., Wosiński T., Mąkosa A., Skierbiszewski C., Grzegory I., Perlin P.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

331-337

EN

We present results of deep-level transient spectroscopy investigations of defects in a GaN-based heterostructure of a blue-violet laser diode, grown by plasma-assisted molecular beam epitaxy on a bulk GaN substrate. Three majority-carrier traps, T1 at E_C - 0.28 eV, T2 at E_C - 0.60 eV, and T3 at E_V + 0.33 eV, were revealed in deep-level transient spectra measured under reverse-bias conditions. On the other hand, deep-level transient spectroscopy measurements performed under injection conditions, revealed one minority-carrier trap, T4, with the activation energy of 0.20 eV. The three majority-carrier traps were revealed in the spectra measured under different reverse-bias conditions, suggesting that they are present in various parts of the laser-diode heterostructure. In addition, these traps represent different charge-carrier capture behaviours. The T1 trap, which exhibits logarithmic capture kinetics, is tentatively attributed to electron states of dislocations in the n-type wave-guiding layer of the structure. In contrast, the T2, T3, and T4 traps display exponential capture kinetics and are assigned to point defects.

7

Observation of Magnetic Anisotropy in GaN:Cr Single Crystals

40%

Gosk J., Boćkowski M., Kowalski G., Grzegory I., Szczytko J., Twardowski A.

Acta Physica Polonica A

|

2012

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vol. 122

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issue 6

1007-1009

EN

Magnetic properties of bulk wurtzite GaN:Cr single crystals were studied with the magnetic field applied parallel and perpendicular to the crystal wurtzite c-axis. Structure of the crystal was examined by the X-ray diffraction method. Strong anisotropy of magnetization at low temperatures (2-10 K) was observed. The experimental data suggest Cr to be in nonspherical d^4 configuration.

8

Luminescence Dynamics of Exciton Replicas in Homoepitaxial GaN Layers

40%

Korona K., Baranowski J., Pakuła K., Monemar B., Bergman J., Grzegory I., Porowski S.

Acta Physica Polonica A

|

1997

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vol. 92

|

issue 4

841-844

EN

Photoluminescence of excitons and their phonon replicas in homoepitaxial MOCVD-grown gallium nitride (GaN) layers have been studied by picosecond (ps) time-resolved photoluminescence spectroscopy. The time-resolved photoluminescence spectroscopy has shown that the free excitons and their replicas have the fastest dynamics (decay time of about 100 ps). Then, the excitons-bound-to-donors emission rises (with the rise time similar to the free excitons decay time) and decays with t=300 ps. The excitons-bound-to-acceptors has the slowest decay (about 500 ps). It has been found that the ratio of excitons-bound-to-acceptors and excitons-bound-to-donors amplitudes and their decay times are different for 1-LO replicas and then for zero-phonon lines, whereas the ratio of amplitudes and the decay time of the 2-LO replicas are similar to the ones of the zero-phonon lines.

9

High Pressure Freeze-out of Electrons in Undoped GaN Crystal. Proof of Existence of Resonant Donor State (Nitrogen Vacancy)

40%

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

Photoluminescence Study of Bulk GaN Doped with Beryllium

40%

Jaworek M., Wysmołek A., Kamińska M., Twardowski A., Boćkowski M., Grzegory I.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

705-710

EN

Photoluminescence of bulk GaN:Be grown by high pressure method is presented. The investigated crystals show well-resolved photoluminescence due to free and bound excitons similar to that observed for homoeptitaxial GaN layers. In addition to the excitonic transitions, pronounced luminescence band at 3.38 eV, due to Be acceptor, is observed. It was found that temperature behavior of this emission is typical of donor- and conduction band-acceptor transitions. The optical activation energy of Be acceptor is obtained to be of 60±15 meV.

11

Two-Electron Transition in Homoepitaxial GaN Layers

40%

Fiorek A., Baranowski J., Wysmołek A., Pakuła K., Wojdak M., Grzegory I., Porowski S.

Acta Physica Polonica A

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1997

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vol. 92

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issue 4

742-744

EN

It is shown that the luminescence mapping is a powerful method to help identify optical transitions. Two-electron transition was identified in the homoepitaxial GaN layer by this technique. It was found that the donor and acceptor bound exciton emissions are spatially displaced and show intensity maxima at different places of the epitaxial layer. It was also found that the 3.45 eV line, suspected as "two-electron transition", follows exactly the donor bound exciton spatial distribution. Donor bound exciton recombines leaving the neutral donor in the excited 2s state. Thus, 1s-2s excitation being equal to 22 meV corresponds to 29 meV hydrogenic donor binding energy. This is the first identification of the two-electron transition in GaN.

12

Time-Resolved Studies of Gallium Nitride Doped with Gadolinium

40%

Witek B., Wysmołek A., Kamińska M., Twardowski A., Potemski M., Boćkowski M., Grzegory I.

Acta Physica Polonica A

|

2008

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vol. 114

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issue 5

1425-1430

EN

Time-resolved photoluminescence experiments on high quality bulk GaN doped with Gd are presented. It was found that the decay time of Gd-related transitions observed for 4.2 K around 1.78 eV is of about 3 ms. Such a long decay time strongly supports the identification of this emission band as due to transitions between Gd³+(4f⁷) levels. The decay time measured for Gd-related transitions observed in the UV spectral range, close to the GaN band-gap, was found to be much faster than 1 μs. This suggests that these emission lines could hardly be correlated with internal transitions within Gd³+(4f⁷). Possible origin of the Gd-related UV luminescence is discussed.

13

Measurement of Very Small Zeeman Splittings in GaN:Mn,Mg by Faraday Rotation

33%

Wołoś A., Kossacki P., Golnik A., Kamińska M., Gaj J., Twardowski A., Grzegory I., Boćkowski M., Porowski S.

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issue 4-5

695-699

EN

In this work we demonstrate an application of Faraday rotation for measuring an extremely small Zeeman splitting of an Mn related absorption line placed at 1.417 eV in optical absorption spectrum of Mn and Mg doped gallium nitride. Analysis of the collected spectra allowed us to determine the value of the splitting as equal to 0.12±0.01 meV at 6 T. This data should help in establishing the nature of the observed absorption band.

14

Coupling of LO Phonons to Excitons in GaN

33%

Wysmołek A., Łomiak P., Baranowski J., Pakuła K., Stępniewski R., Korona K., Grzegory I., Boćkowski M., Porowski S.

Acta Physica Polonica A

|

1996

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vol. 90

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issue 5

981-984

EN

The photoluminescence of homoepitaxial and heteroepitaxial GaN layers is reported. It is shown that the coupling between LO phonons and neutral acceptor bound excitons is much stronger than the coupling between LO phonons and neutral donor bound excitons. In undoped homoepitaxial layer, in spite of that the no-phonon emission due to donor bound excitons is one order of magnitude stronger than the acceptor bound excitons emission, the predominant structure in the LO phonon replica of the excitonic spectrum is related to optical transitions involving acceptor bound excitons. Temperature studies showed that at higher temperature the LO phonon replica is related to free excitons.

15

MnAs Overlayer on GaN(000_1)-(1 x 1) - Its Growth, Morphology and Electronic Structure

33%

Kowalski B., Kowalik I., Iwanowski R., Łusakowska E., Sawicki M., Sadowski J., Grzegory I., Porowski S.

Acta Physica Polonica A

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2004

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vol. 105

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issue 6

645-650

EN

MnAs layer has been grown by means of MBE on the GaN(000_1)-(1 x 1) surface. Spontaneous formation of MnAs grains with a diameter of 30-60 nm (as observed by atomic force microscopy) occurred for the layer thickness bigger than 7 ML. Ferromagnetic properties of the layer with Curie temperature higher than 330 K were detected by SQUID measurements. Electronic structure of the system was investigated in situ by resonant photoemission spectroscopy for MnAs layer thickness of 1, 2, and 8 ML. Density of the valence band states of MnAs and its changes due to the increase in the layer thickness were revealed.

16

Growth of GaN Metalorganic Chemical Vapour Deposition Layers on GaN Single Crystals

33%

Pakula K., Baranowski J. M., Stępniewski R., Wysmołek A., Grzegory I., Jun J., Porowski S., Sawicki M., Starowieyski K.

Acta Physica Polonica A

|

1995

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vol. 88

|

issue 5

861-864

EN

The homoepitaxial growth of GaN layers has been achieved for the first time. Bulk GaN single crystals which have been used as a substrate have been grown from diluted solution of atomic nitrogen in the liquid gallium at 1600°C and at nitrogen pressure of about 15-20 kbar. It is shown that a terrace growth of GaN epitaxial layer has been realized. The high quality of the GaN film has been confirmed by luminescence measurements. The analysis of donor-acceptor and exciton luminescence is presented.

17

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

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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

Photoluminescence and Electron Paramagnetic Resonance Studies of Bulk GaN Doped with Gadolinium

33%

Lipińska Z., Pawłowski M., Żołnierowicz H., Wysmołek A., Palczewska M., Kamińska M., Twardowski A., Boćkowski M., Grzegory I.

Acta Physica Polonica A

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2006

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vol. 110

|

issue 2

243-248

EN

Photoluminescence and electron paramagnetic resonance experiments on strain free GaN bulk crystals of wurtzite structure doped with gadolinium are reported. Efficient gettering of residual GaN donors by Gd was observed. Electron paramagnetic resonance showed that Gd ion incorporated into GaN lattice had Gd^{3+}(4f^7) configuration. The observed photoluminescence spectra were explained as due to intracenter Gd^{3+}(4f^7) transitions. No ferromagnetic behavior was detected.

19

III-V Semiconducting Nitrides Energy Gap under Pressure

33%

Perlin P., Gorczyca I., Teisseyre H., Suski T., Litwin-Staszewska E., Porowski S., Grzegory I., Christensen N.

Acta Physica Polonica A

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1992

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vol. 82

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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.

20

Magnetoluminescence Studies of GaN:Fe

33%

Niedźwiadek A., Wysmołek A., Wasik D., Potemski M., Szczytko J., Kamińska M., Twardowski A., Łucznik B., Pastuszka B., Grzegory I.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

177-182

EN

We report on magneto-optical studies on iron doped GaN crystals grown using hydride vapor phase epitaxy method on bulk GaN substrate. The investigated samples showed an intensive 1.3 eV luminescence band, characteristic of Fe^{3+}(d^5) center in GaN. A high quality of the investigated samples allowed us to observe a well-resolved fine structure of intracenter transitions between ^4T_1(G) and ^6A_1(S) states, consisting of four sharp no-phonon lines. All the observed no-phonon lines showed pronounced splittings in magnetic field. From the analysis of the magneto-optical data, the structure of split ^4T_1(G) multiplet in the magnetic field applied along c-axis of GaN crystals was established.

Refine search results

Application of GaN Pressure Grown Crystals for Epitaxy of GaN-Based Structures

The Application of High Pressure in Physics and Technology of III-V Nitrides

Observation of Magnetic Anisotropy in Bulk GaMnN:Mg Crystals

Crystallographic Properties of Bulk GaN Crystals Grown at High Pressure

Band Structure and Refractive Index of Gallium Nitride Under Pressure

Deep-Level Defects in MBE-Grown GaN-Based Laser Structure

Observation of Magnetic Anisotropy in GaN:Cr Single Crystals

Luminescence Dynamics of Exciton Replicas in Homoepitaxial GaN Layers

High Pressure Freeze-out of Electrons in Undoped GaN Crystal. Proof of Existence of Resonant Donor State (Nitrogen Vacancy)

Photoluminescence Study of Bulk GaN Doped with Beryllium

Two-Electron Transition in Homoepitaxial GaN Layers

Time-Resolved Studies of Gallium Nitride Doped with Gadolinium

Measurement of Very Small Zeeman Splittings in GaN:Mn,Mg by Faraday Rotation

Coupling of LO Phonons to Excitons in GaN

MnAs Overlayer on GaN(000_1)-(1 x 1) - Its Growth, Morphology and Electronic Structure

Growth of GaN Metalorganic Chemical Vapour Deposition Layers on GaN Single Crystals

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

Photoluminescence and Electron Paramagnetic Resonance Studies of Bulk GaN Doped with Gadolinium

III-V Semiconducting Nitrides Energy Gap under Pressure

Magnetoluminescence Studies of GaN:Fe