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1

The Symmetry of the EL2 Defect in the Metastable State

100%

Trautman P., Baranowski J.

Acta Physica Polonica A

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1992

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vol. 82

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issue 4

609-612

EN

We measured recovery of the optical absorption of EL2 under [100] and [111] uniaxial stress during heating of the crystal. The recovery step, occurring at about 45 K in n-type GaAs, splits into two components under [111] stress, and no splitting is observed under [100] stress. The same behavior under uniaxial stress shows the recovery occurring at 125 K in semi-insulating GaAs. A fraction of centers recovering at lower temperature can be altered by excitation of metastability with polarized light or by excitation under stress. These results indicate that EL2 in the metastable state is trigonally distorted from the tetrahedral symmetry of the ground state.

2

Light Induced Ordering of the EL2 Defects in the Metastable State

100%

Trautman P., Baranowski J.

Acta Physica Polonica A

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1993

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vol. 84

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issue 4

677-680

EN

We tried to detect a strain in the crystal induced by the ordering of the EL2 defects in the metastable state by measuring linear dichroism and birefringence. We found that this strain is below the detection limit of our experiments and lower than that induced by 1 MPa of external stress. The observed dependence of orientation of the EL2 defects in the metastable state on the polarization of light used to transform EL2 to the metastable state is consistent with the attribution of the metastability of EL2 to the transformation of the isolated As_{Ga} to the V_{Ga}A_{Si} defect and is in conflict with the As_{Ga}-A_{Si} defect pair model of EL2.

3

An Estimate of the Energy Gap of InN from Measurements of the Fundamental Absorption Edge

81%

Trautman P., Pakuła K., Witowski A., Baranowski J.

Acta Physica Polonica A

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2005

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vol. 108

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issue 5

903-908

EN

Optical absorption between 0.4 and 4.5 eV of an InN layer grown by metalorganic vapour phase epitaxy on sapphire was measured at 296 and 12 K. The layer was also characterized by measurements of the Hall effect and of infrared reflectivity in the region of the plasma edge, which determined the concentration, mobility, and effective mass of electrons in the conduction band. The energy gap of InN was estimated to be equal to 0.9±0.2 eV. It was obtained from the spectral position of the fundamental absorption edge. Corrections to the energy gap resulting from the broadening of the fundamental absorption edge, from the Burstein-Moss shift, and from a band-gap shrinkage due to the impurity potential were included.

4

High Resistivity GaN Single Crystalline Substrates

42%

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

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1997

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vol. 92

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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.

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4 Acta Physica Polonica A

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2 Pakuła K.

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1 Grzegory I.

1 Leszczyński M.

1 Litwin-Staszewska E.

1 Porowski S.

1 Suski T.

1 Teisseyre H.

1 Witowski A.

1 Wróblewski M.

1 Łucznik B.

The Symmetry of the EL2 Defect in the Metastable State

Light Induced Ordering of the EL2 Defects in the Metastable State

An Estimate of the Energy Gap of InN from Measurements of the Fundamental Absorption Edge

High Resistivity GaN Single Crystalline Substrates