Wyniki wyszukiwania - Biblioteka Nauki

1

Light Induced Recovery of EL2 Defect from the Metastable Configuration

100%

Teisseyre H. , Kuszko W.

Acta Physica Polonica A

|

1991

|

tom 79

|

nr 2-3

267-270

EN

The measurements: of changes in a magnitude of ΕL2 characteristic infrared absorption were used to investigate a phenomenon of light induced recovery of the defect from its metastable state in semi-insulating (SI) and n-type GaAs. At a temperature of 12K illumination with photons of energy 1.45 eV caused partial recovery for both SI and n-type samples. For n-type samples partial recovery occurred also after irradiation with photons of energy lower than 0.73 eV.

2

Pressure Dependence of Exciton Binding Energy in GaN/Al_{x}Ga_{1 - x}N Quantum Wells

80%

Bardyszewski W. , Łepkowski S. , Teisseyre H.

Acta Physica Polonica A

|

2011

|

tom 119

|

nr 5

663-665

EN

We present a theoretical study of excitons in GaN/Al_{x}Ga_{1 - x}N wurtzite (0001) quantum wells subjected to hydrostatic pressure. Our results show that the combined effect of pressure induced changes in band structure and piezoelectric field leads to reduction of the exciton binding energy. This subtle effect is described quite accurately by our multiband model of excitons in quantum wells.

3

Effect of the Built-In Strain on the In-Plane Optical Anisotropy of m-Plane GaN/AlGaN Quantum Wells

80%

Łepkowski S. , Bardyszewski W. , Teisseyre H.

Acta Physica Polonica A

|

2011

|

tom 120

|

nr 5

897-898

EN

We study theoretically the influence of the anisotropic biaxial strain originating from the lattice mismatch between the m-plane GaN/AlGaN quantum wells structure and the substrate on the optical anisotropy of such systems. It is demonstrated that the oscillator strengths for optical transitions with polarization of light parallel and perpendicular to the crystal axis c strongly depend on strain to such an extent that, by increasing the concentration of Al in the substrate from x = 0 to x = 0.5 one can change the polarization of the emitted light with respect to the c-axis by 90 degrees.

4

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

61%

Perlin P. , Teisseyre H. , Suski T. , Leszczyński M. , Grzegory I. , Jun J. , Porowski S.

Acta Physica Polonica A

|

1995

|

tom 87

|

nr 1

141-143

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.

5

Band Structure and Refractive Index of Gallium Nitride Under Pressure

61%

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

Acta Physica Polonica A

|

1991

|

tom 80

|

nr 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

III-V Semiconducting Nitrides Energy Gap under Pressure

51%

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

Acta Physica Polonica A

|

1992

|

tom 82

|

nr 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.

7

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

51%

Teisseyre H. , Perlin P. , Leszczyński M. , Suski T. , Dmowski L. , Grzegory I. , Porowski S. , Jun J. , Moustakas T.

Acta Physica Polonica A

|

1995

|

tom 87

|

nr 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.

8

High Resistivity GaN Single Crystalline Substrates

41%

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

|

tom 92

|

nr 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.

9

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

41%

Teisseyre H. , Szymański M. , Khachapuridze A. , Skierbiszewski C. , Feduniewicz-Żmuda A. , Siekacz M. , Łucznik B. , Kamler G. , Kryśko M. , Suski T. , Perlin P. , Grzegory I.

Acta Physica Polonica A

|

2007

|

tom 112

|

nr 2

467-472

EN

The intention of this work is to discuss and report on our research on nonpolar laser structures grown on bulk GaN crystal substrates along the (11¯20) nonpolar direction. The main advantages of such nonpolar structures are related to the elimination of the built-in electric fields present in commonly used systems grown along the polar (0001) axis of nitride crystals. We demonstrated the optically pumped laser action on separate confinement heterostructures. Laser action is clearly shown by spontaneous emission saturation, abrupt line narrowing, and strong transversal electric polarization of output light. The lasing threshold was reached at an excitation power density of 260 kW/cm^2 for a 700μm long cavity (at room temperature).

10

Thermal Expansion of GaN Bulk Crystals and Homoepitaxial Layers

41%

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

|

1996

|

tom 90

|

nr 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.