Photoluminescence of dome and hut shaped Ge(Si) self-assembled islands embedded in a tensile-strained Si layer
М. В. ШалеевА. В. НовиковArtem N. YablonskiyYu. N. DrozdovД. Н. ЛобановZ. F. Krasil’nikO. A. Kuznetsov
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The effect of the growth temperature (Tg) on photoluminescence of Ge(Si) self-assembled islands embedded between tensile-strained Si layers was studied. The observed redshift of the photoluminescence peak of the dome islands with a decrease of Tg from 700to630°C is associated with an increase of Ge content in the islands and with the suppression of smearing of the strained Si layers. The blueshift of the photoluminescence peak with a decrease of Tg from 630to600°C is associated with a change of the type of islands on surface, which is accompanied by a decrease in islands’ height.Keywords:
Blueshift
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Photoluminescence (PL) properties of blue InGaN quantum-well light-emitting diodes have been investigated at 20 K as a function of excitation power and reverse bias voltage (external field). PL intensity reduction of the main blue emission band is observed by increasing the reverse field. The photoexcitation power dependence suggests that the hole escape process plays an important role for the determination of PL intensity under the reverse bias conditions.
Photoexcitation
Wide-bandgap semiconductor
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The photoluminescence properties of hollow ZnS microspheres with different sizes and shell thickness were studied. There exist two emission bands situated in blue and green regions in the photoluminescence spectra of the microspheres: the green band has a red shift with increasing the excitation power at different temperatures, while the blue band has a blue shift at room temperature and without any changes excited at 83 K. The green emission has a normal red shift while the blue emission shows an abnormal red-blue shift with increasing temperature. The origins of anomalous photoluminescence properties were analysed and discussed in terms of the carrier localisation at the defect levels.
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Red shift
Stokes shift
Photoluminescence excitation
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This work investigates the photoluminescence properties of Zn1−xMgxO–ZnO single quantum wells, which have been fabricated by molecular-beam epitaxy. With increasing temperature from 13to300K the single quantum well-related emission peaks exhibit an irregular S-shaped (redshift-blueshift-redshift) behavior, which is in contrast with that ascribed to band gap shrinkage (redshift). In order to clarify the origin of this behavior, the temperature dependence of the integral photoluminescence intensity of the quantum well emission was studied and the relevant activation energies were calculated and correlated to its full width at half maximum, band offsets, and monolayer fluctuations.
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Wide-bandgap semiconductor
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Abstract Growth of germanium or silicon-germanium on silicon 100 surfaces produces pyramid shaped islands after several monolayers of coverage. With further deposition, these islands will continue to grow until they reach a critical volume where a transition to a dome shape occurs. The critical surface coverage for island formation and the critical volume for the pyramid to dome transition depend upon the silicon to germanium ratio or degree of mismatch between the deposited material and the silicon substrate. Strain plays a dominant role in the shape transitions. Annealing studies have shown that the pyramid to dome transition.is reversible and is likely due to strain reduction related to interdiffusion. Annealing results in island growth, a decrease in the number of islands, and interdiffusion of the silicon and germanium. The interdiffusion relieves the strain and shifts the critical volume to a value exceeding the current volume of the dome shaped island thereby driving the transition back to pyramidal shape.
Interface (matter)
Silicon valley
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Luminescent SiO2 films containing Ge nanocrystals (nc-Ge) are fabricated by Ge+ ion implantation and thermal annealing. The nc-Ge density is controlled by the implanted Ge+ dose. Under ultraviolet excitation, the films exhibit two photoluminescent (PL) bands simultaneously in the violet–blue region. With increasing annealing temperature (Tan) in the range of 1100 °C, the relative ratio of the intensities of the two PL bands increases slightly from 2.3 to 3 for the films with a dose of 1×1016 cm−2, whereas it increases remarkably from 2.8 to 4.5 for films with a dose of 1×1017 cm−2. On the other hand, the PL integrated intensities of the two kinds of films reach their maxima at Tan of 900 and 700 °C, respectively. It is proposed that the two PL bands are due to germanium-related oxygen-deficient centers. The annealing characteristics are explained well.
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We show that there is no correlation between the blue shift of the visible photoluminescence band and red shift of the Raman phonon line in porous silicon, in contrast to the recently reported results. We also report a drastic red shift of the photoluminescence peak position with pressure up to 6 GPa and show that this is much larger than that of the crystalline silicon. These observations cast doubt on the suggested mechanism of quantum size effects in porous silicon.
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We investigated the influence of a μ-pixelated chip process on the photoluminescence (PL) and electroluminescence (EL) of a monolithic InGaN/GaN based blue light emitting diode with a continuous n-GaN layer. Particularly, we observed the impact of the metallic p-contact on the PL emission wavelength. A PL wavelength shift in the order of 10 nm between contacted and isolated areas was assigned to screening of internal piezoelectric fields due to charge carrier accumulation. μPL and μEL mappings revealed correlated emission wavelength and intensity inhomogeneities, caused by the epitaxial growth process. The edges of single pixels were investigated in detail via resonant confocal bias-dependent μPL. No influence on the intensity was observed beyond 300 nm away from the edge, which indicated a good working edge passivation. Due to the low lateral p-GaN conductivity, the μPL intensity was enhanced at isolated areas.
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Blueshift
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The effect of the growth temperature (Tg) on photoluminescence of Ge(Si) self-assembled islands embedded between tensile-strained Si layers was studied. The observed redshift of the photoluminescence peak of the dome islands with a decrease of Tg from 700to630°C is associated with an increase of Ge content in the islands and with the suppression of smearing of the strained Si layers. The blueshift of the photoluminescence peak with a decrease of Tg from 630to600°C is associated with a change of the type of islands on surface, which is accompanied by a decrease in islands’ height.
Blueshift
Dome (geology)
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Dome (geology)
Blueshift
Atmospheric temperature range
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