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Time Resolved Magnetophotoluminescence of Biased GaAs/AlGaAs Double Quantum Well Structure

100%
Surowiecka K., Wysmołek A., Stępniewski R., Potemski M., Henini M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1369-1374
EN
Time resolved photoluminescence of double quantum well structure was investigated versus electric and magnetic fields applied across the sample. The emission due to direct excitons (electron and hole are localized within the same quantum well) decays fast at the nanosecond timescale, whereas the recombination kinetics of indirect excitons is much slower and spreads over microseconds. The time evolution of indirect exciton emission is shown to be altered by application of either electric or magnetic field. This reflects the non-trivial effects of exciton localization which leads to the non-exponential decays of the indirect exciton emission.
2
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Temporal Evolution of Multi-Carrier Complexes in Single GaN/AlGaN Quantum Dots

86%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
879-884
EN
Microphotoluminescence of low-density GaN/Al_xGa_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The narrow lines in the microphotoluminescence spectra due to the single quantum dots are observed. Both energy and intensity of these lines show temporal fluctuations. Statistical analysis based on the correlation matrix allowed us to identify objects, which are affected by photo-induced electric field fluctuations. Relations between emission lines participating in the spectrum are discussed.
3
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Single GaN/AlGaN Quantum Dot Spectroscopy

86%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
233-236
EN
Microphotoluminescence of low-density GaN/Al_{x}Ga_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The detailed analysis of the emission from these structures enables the observation of pairs of lines separated by the energy up to 3 meV. They behave in a different way under different excitation power that suggests that this doublet structure can be associated with the exciton and trion (or biexciton recombination). It is observed that for different quantum dots the energy of the charged exciton complex emission could be higher or lower than the neutral exciton one. It is discussed in terms of a competition between attractive e-h and repulsive e-e (h-h) Coulomb interaction that occurs because of the existence of the built-in electric field that separates electrons and holes in the dot.
4
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Time Evolution of the Microluminescence Energy οf GaN/AlGaN Quantum Dots

86%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
933-935
EN
Time evolution of the microphotoluminescence from low-density GaN/Al_{x}Ga_{1-x}N quantum dots grown by metal organic chemical vapor deposition using in situ etching of AlGaN is presented. The observed effect is related to the energy changes that begin immediately after sample illumination with the exciting laser light and saturate after some time. Typically, the luminescence energy decreases and the change is exponential with characteristic times in a range between several dozen and several hundred seconds. However, sometimes we observed the energy increase with characteristic times in a range between several and a few hundred seconds. The obtained results are discussed in terms of the metastable change of the electric field, induced by spontaneous polarization present in GaN/AlGaN structure (in the growth direction), and strain- or defect-induced changes of the electric field in the vicinity of the dot.
5
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InGaN QW in External Electric Field Controlled by Pumping of 2D-Electron Gas

86%
Korona K., Drabińska A., Surowiecka K., Wołowiec L., Borysiuk J., Caban P., Strupiński W.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1179-1186
EN
We present investigations of GaInN/GaN/AlGaN structure containing cavity designed so that the electric field inside it can be changed by illumination. Numerical calculations show that illumination can change carrier distributions and consequently change the field and potential. The electric field influences properties of a quantum well placed in the cavity. We confirmed experimentally that the electric field controlled by external bias or by optical pumping, can change energy and occupation of electronic states in the quantum well. The quantum well energy could be changed of about 80 meV by voltage and 15 meV by illumination.
6
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Potential and Carrier Distribution in AlGaN Superlattice

73%
Korona K., Pakuła K., Bożek R., Drabińska A., Surowiecka K., Stępniewski R., Zielińska-Rohozińska E., Baranowski J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 4
723-729
EN
Photocurrent spectroscopy and Kelvin force microscopy have been used in order to determine charge, field, and potential distributions in spontaneously grown superlattice. The spectra show that light can generate currents and potentials in both directions depending on photon energy. A numerical model made for superlattice of periodλ_{SL} = 33 nm shows that electric field in superlattice oscillates coherently with Al content. The oscillations of electric field explain the different directions of photocurrent. The electric field can also separate electrons and holes, making carrier lifetimes longer and lowering excitation intensity threshold for occupation inversion.
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