Prof. Izabella GRZEGORY

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Academic Career Length

42Years (1985-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

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15 March 1996 in Journal of Applied Physics

Journal Article

Elastic constants of gallium nitride

A. Polian

M. Grimsditch

Izabella GRZEGORY

The elastic constants of GaN have been determined using Brillouin scattering; in GPa they are: C11=390, C33=398, C44=105, C66=123, C12=145, and C13=106. Our values differ substantially from those quoted in the literature which were obtained from the determination of mean square displacement of atoms measured by x-ray diffraction.

1 January 1992 in Physical Review B

Journal Article

Raman scattering and x-ray-absorption spectroscopy in gallium nitride under high pressure

Perlin Piotr

Claude Jauberthie-Carillon

Jean Paul Itie

Alfonso San-Miguel

Izabella GRZEGORY

Alain Polian

Gallium nitride was studied by Raman scattering and x-ray-absorption spectroscopy up to 60 GPa. A high-pressure structural phase transition was observed in gallium nitride at 47 GPa by means of Raman scattering and x-ray-absorption spectroscopy. We also report the direct determination of the bulk modulus

B_{0}

of this compound (245 GPa). Grüneisen parameters of the four observed phonon modes were established. The transition pressure is compared with existing calculations.

20 October 1997 in Physical Review Letters

Journal Article

Observation of Native Ga Vacancies in GaN by Positron Annihilation

K. Saarinen

T. Laine

S. Kuisma

J. Nissilä

P. Hautojärvi

S. Porowski

Positron annihilation experiments were performed to identify native point defects in n-type GaN bulk crystals as well as in epitaxial layers. The results show that Ga vacancies are present at concentrations

10^{17} - 10^{18} {cm}^{- 3}

in both GaN bulk crystals and layers. The Ga vacancies are negatively charged, and their concentration correlates with the intensity of the yellow luminescence. We conclude that the Ga vacancies contribute to the electrical compensation of n-type GaN and that their acceptor levels are involved in the yellow luminescence transition.

1 July 1996 in Applied Physics Letters

Journal Article

Lattice parameters of gallium nitride

M. Leszczynski

Teisseyre Henryk

T. Suski

Izabella GRZEGORY

M. Bockowski

T. S. Cheng

Lattice parameters of gallium nitride were measured using high-resolution x-ray diffraction. The following samples were examined: (i) single crystals grown at pressure of about 15 kbar, (ii) homoepitaxial layers, (iii) heteroepitaxial layers (wurtzite structure) on silicon carbide, on sapphire, and on gallium arsenide, (iv) cubic gallium nitride layers on gallium arsenide. The differences between the samples are discussed in terms of their concentrations of free electrons and structural defects.

10 July 1995 in Physical Review Letters

Journal Article

Towards the Identification of the Dominant Donor in GaN

Perlin Piotr

T. Suski

Teisseyre Henryk

M. Leszczynski

Izabella GRZEGORY

T. D. Moustakas

We analyze optical absorption, transmission, luminescence, and Raman scattering in

n

-type GaN at hydrostatic pressures up to 30 GPa. The results show freeze-out of free electrons above

\sim 20 GPa

due to trapping at levels that are resonant at ambient pressure but become gap states at high pressures. Ab initio calculations show that both the N vacancy and the Ga interstitial undergo this transition at

\sim 20 GPa

, but the vacancy should be more abundant. The pressure dependence of the yellow luminescence indicates that a transition between a shallow donor and a deep acceptor is involved.

15 July 1999 in Physical Review B

Journal Article

Photoluminescence and reflectance spectroscopy of excitonic transitions in high-quality homoepitaxial GaN films

K. Kornitzer

T. Ebner

K. Thonke

R. Sauer

C. Kirchner

S. Porowski

We report on highly resolved photoluminescence (PL) and reflectance (RF) spectra of a homoepitaxial GaN layer grown by metal-organic vapor phase epitaxy. This sample exhibits narrow linewidths of several PL emission peaks, down to

\approx 100 μ eV

full width at half maximum for some bound exciton transitions. As a consequence, we have detected new PL features as, e.g., a fivefold fine structure of the donor-bound exciton line at

\approx 3.471 eV,

and other known PL transitions could be determined with high precision. In RF measurements, the extraordinary quality of the epitaxial layer allowed observation of weakly damped excitonic ground-state transitions and of narrow excited exciton transitions with high signal-to-noise ratio.

About Me

Prof. Dr. Izabella Grzegory graduated from the Electrotechnical Institute, St. Petersburg, in 1983, and earned her PhD and completed her habilitation at the Institute of Physics Polish Academy of Sciences, Warsaw, Poland. She has been working for the Institute of High Pressure Physics PAS, Warsaw, Poland, since 1983 and as director of the Institute since 2011. Her main scientific interest is the growth of semiconductor crystals, especially gallium nitride (GaN), in very-high-pressure nitrogen. In 1995, she received the Jamieson Award (International) for Best PhD Thesis in High Pressure Science and Technology and Second Prize in the Prof. G. Bialkowski Competition for Best Polish PhD Thesis in Mathematics and Physics in 1995. She was an elected member of the AIRAPT Executive Committee in 2009.

Prof. Izabella GRZEGORY

Prof. Izabella GRZEGORY

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