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1
Content available remote

Field Emission Study of Germanium Thin Films on a Niobium Surface

100%
Bakhtizin R., Suvorov A., Zaripov R.
Acta Physica Polonica A
|
1992
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vol. 81
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issue 2
247-255
EN
The behaviour of germanium on atomically clean niobium single crystal planes has been studied by probe-hole field emission microscopy as well as by means of the spectral analysis of field emission current fluctuations. Variations of average work function, surface diffusion activation energies, and slopes of the spectral density function with different coverages and substrate temperatures are measured.
2
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Thermal Donor Generation in Boron- and Aluminium-Doped Czochralski Silicon

63%
Kopalko K., Kaczor P., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1991
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vol. 80
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issue 3
345-348
EN
Generation of thermal donor centres in oxygen-rich silicon doped with boron and aluminium acceptors has been studied with the FTIR technique. It has been found that upon annealing 470°C two kinds of absorption series were generated. One of them belonged to the well-known first ionization level of silicon thermal (double) donors (TD's): TD°/TD^{+} . The second series was identified with the so-called shallow thermal donors (STD's). The generation kinetics of the two series was followed for both kinds of acceptor doping and significant differences has been found. The results of the FTIR investigations were further compared with the magnetic resonance findings allowing for their mutual correlation and more general conclusions.
3
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Infrared Absorption Study of Thermally Generated Shallow Donor Centers in Czochralski Silicon

63%
Kaczor P., Kopalko K., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1992
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vol. 82
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issue 4
677-680
EN
A comparative study of thermally generated donor centers in boron and aluminum doped Czochralski silicon was performed by means of Fourier transform infrared technique. A detailed study revealed presence of donor centers belonging to the well-known series of thermal donors and shallow thermal donors. For both types of material the same centers could be observed while considerable differences in their generation kinetics occurred. In addition to the previously identified species also new ones could be observed. One of them, with single ionization level at approximately 39.5 meV, was found to exhibit clear dependence of its concentration upon illumination of the sample during cooling from room temperature to liquid He temperature.
4
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Light Induced Recovery of EL2 Defect from the Metastable Configuration

63%
Teisseyre H., Kuszko W.
Acta Physica Polonica A
|
1991
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vol. 79
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issue 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.
5
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Bistable Behaviour of the New Shallow Thermal Donor in Aluminum Doped Silicon

63%
Kaczor P., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1993
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vol. 84
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issue 3
555-558
EN
In the present study a new bistable shallow thermal donor in aluminum doped silicon was investigated by means of the Fourier transform infrared spectroscopy. The temperature dependence of the photo-conversion into the metastable state was established and some Hints for the origin of the metastability were given.
6
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High Pressure Far-Infrared Magnetooptical Studies of Sn and S Donors in GaAs

63%
Dmochowski J., Wang P., Stradling R.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 2
279-282
EN
The diamond anvil cell technique is applied for magneto-optical far-infrared transmission experiments with LPE grown GaAs:Sn. The 1s-2p(+) intra-shallow-Γ-donor transition is investigated as a function of high hydrostatic pressure for Sn and residual S donors. Both donors are shallow up to 30 kbar. Above this pressure both donors become deep and shallow donor absorption is persistently bleached due to deep non-metastable (non DX-like) states of the donors entering the gap of GaAs.
7
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Interaction of Excitons Bound to 3d Transition Metal Ions with Lattice Vibrations in II-VI Semiconductors

63%
Sokolov V., Surkova T.
Acta Physica Polonica A
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1991
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vol. 79
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issue 1
155-157
EN
The analysis of an interaction of bound excitons with lattice vibrations for ZnO:Ni and ZnO:Cu is given on the basis of symmetry consideration.
8
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Acceptor-Like Level of the EL2 Defect in its Metastable Configuration

63%
Dreszer P., Baj M., Babiński A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 1
129-132
EN
This paper presents for the first time the evident experimental confirmation that EL2 defect, while being in its metastable configuration, traps under hydrostatic pressure an additional electron, i.e. the acceptor-like (EL2*)^{0/-} level enters the energy gap under pressure. We propose that in n-GaAs the EL2 thermal recovery takes always place via the (EL2*)^{-} state.
9
Content available remote

Energy States of Ni in Zn_{1-x}Mn_{x}Se:Ni Solid Solutions

63%
Permogorov S., Tenishev L., Sokolov V., Surkova T.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
705-708
EN
Absorption and reflectivity measurements were carried out on Zn_{1-x}Mn_{x}Se:Ni solid solutions. The spectra demonstrate the radical change of the structure of internal Ni^{2+}(3d^{8}) transitions at the presence of the Mn ions and strong dependence on Mn concentration. The threshold energy ħω_{th} for the process of Ni photoionization to the valence band Ni^{2+}(3d^{8}) + ħω_{th} → Ni^{1+}(3d^{9}) + h is shifted to the lower energy by 30 meV, but hardly depends on x despite the essential increase in the energy gap.
10
Content available remote

Electroluminescence from Rare Earth Activated Materials - New Concepts

51%
Godlewski M.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
435-444
EN
The recent progress in the field of thin film electroluminescence devices is reviewed. The mechanisms responsible for rare earth excitation in high electric field electroluminescence structures are explained. A new mechanism including rare earth ionization is described. Processes limiting electroluminescence efficiency are also discussed.
11
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Photoinduced Phenomena in Sulphur Crystals and Films

51%
Dovgii Y., Kityk I., Yablonovska O.
Acta Physica Polonica A
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1992
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vol. 81
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issue 3
405-408
EN
The irradiation of sulphur crystals and films with ultraviolet light induces the change of transmission in the visible part of spectra. It was found that these phenomena exist only at low temperatures (4.2-50 K). The behaviour of optical transparency as a function of time after switching the rumination off was investigated. These dependences are essentially different for the films and crystals. In order to understand the origin of these phenomena the structural investigation was conducted. Very unusual behaviour of darkening kinetics was obtained.
12
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The Symmetry of the EL2 Defect in the Metastable State

51%
Trautman P., Baranowski J.
Acta Physica Polonica A
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1992
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vol. 82
|
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.
13
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Defects Studies in As Grown and Neutron Irradiatcd Phosphorus Rich GaP

51%
Jasiński J., Palczewska M., Korona K., Kamińska M., Bourret E., Elliot G.
Acta Physica Polonica A
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1992
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vol. 82
|
issue 5
829-832
EN
Semi-insulating, p- and n-type liquid encapsulated Czochralski grown phosphorus rich GaP crystals before and alter neutron irradiation were studied. EPR measurements proved that the phosphorus antisite defect P_{Ga} introduced by neutron irradiation was exactly the same as in as grown materials, i.e. surrounded by four substitutional phosphorus atoms. In neutron irradiated crystals EPR showed also a signal, similar to the one found in plastically deformed GaAs and GaP. The concentrations of P_{Ga} and of the other defect were estimated to be of the same order of magnitude. Two absorption bands at 0.81 and 1.12 eV were found for irradiated materials. The temperature dependence of resistivity indicated hopping as the mechanism of conduction in samples irradiated with doses higher than 4 × 10^{16} cm^{-2}.
14
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Hydrogen-Like Excitations of 3d and 4f Isoelectronic Impurities in Semiconductors

51%
Sokolov V.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 2
245-256
EN
In the paper the energy states of structured isoelectronic impurities of transition metals and rare earth elements, donor and acceptor excitons of 3d and 4f impurities, the role of donor and acceptor excitons of 3d and 4f impurities in energy transfer from the matrix to impurities are discussed. It is shown that structured impurities may be classified as "open" and "closed" isoelectronic impurities. The number of electrons in the 3d or 4f shells is changed at hω < E_{g} not changed structure levels generated by forbidden gap properties donor acceptor excitons those energy transfer mechanisms from matrix to an impurity (a capture carriers into 3d or 4f shells open and auger process essentially distinguished two kinds structured isoelectronic for closed impurities a model is discussed in frame which the spectra of electroabsorption photoluminescence cathodoluminescence are described.
15
Content available remote

Optical and Electrical Studies of FR1 and FR2 Defects in GaAs

51%
Dwiliński R., Palczewska M., Kaczor P., Korona K., Wysmołek A., Bożek R., Kamińska M.
Acta Physica Polonica A
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1992
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vol. 82
|
issue 4
613-616
EN
The systematic EPR, optical absorption, photoluminescence and thermally stimulated current studies of acceptor defects in bulk GaAs were performed. For the first time, parallel EPR and optical absorption experiments allowed to find the absorption spectrum due to the photoionization of FR1 defect with the threshold at 0.19 eV. Photoluminescence studies showed two families of bands in the energy range of about 1.25 to 1.35 eV. We tentatively ascribed them to FR1 and FR2 complexes with shallow donors. Thermally stimulated current measurements showed two peaks at 90 K and 110 K assigned to FR1 and FR2 respectively.
16
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Recombination Processes in ZnSe:Eu

51%
Świątek K., Godlewski M.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 3
381-384
EN
The photo-ESR and photoluminescence experiments have been performed on high-resistivity ZnSe:Eu crystals. We report the first evidence that the energy level of Eu^{2+} ground state is located within the ZnSe forbidden gap, approximately 2.1 eV below the bottom of the conduction band.
17
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Magnetotransmission Measurements of Intra-Shallow-Donor Transitions in Semi-Insulating GaAs

51%
Karpierz K., Kożuchowski K., Grynberg M.
Acta Physica Polonica A
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1992
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vol. 82
|
issue 4
617-619
EN
In this paper we present the results of an investigation of the 1s-2p_{+} intra-shallow-donor transition by means of an extremely difficult magnetotransmission experiment performed on semi-insulating GaAs. We report the temperature dependence of the transition intensity. We noticed the absence in the absorbance spectra of a well-pronounced structure which is observed at low magnetic fields in photoconductivity measurements. The results are discussed in terms of a fluctuating potential from ionized centres in semi-insulating GaAs.
18
Content available remote

Iron Impurity Related Optical Transitions in HgSe:Fe

51%
Szuszkiewicz W., Julien C., Balkanski M., Arciszewska M., Witkowska B., Mycielski A.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
437-440
EN
Fe^{2+} crystal field transitions and the heavy hole valence band to the Fe level transitions (e + Fe^{3+} → Fe^{2+}) have been observed and discussed for HgSe doped with iron.
19
Content available remote

Absorption Studies of the Sulphur Donor in GaSb

51%
Kaczor P., Gerrits A., Dobaczewski L., Kaliński Z., Wittlin A.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
399-402
EN
The shallow-deep bistability of the sulphur-related DX centre in GaSb is demonstrated. After photoexcitation of the defect with the near-band gap light the metastable inter-donor transition in the far infrared can be ob­served. This observation allowed us to evaluate the polaron effective mass and polaron coupling constant for the material.
20
Content available remote

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
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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.
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