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| 2. |
- Andreasson, Måns, 1975, et al.
(författare)
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Organic molecular beam deposition system and initial studies of organic layer growth
- 2006
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Ingår i: Physica Scripta. - 1402-4896 .- 0031-8949. ; T126, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- This work describes an organic molecular beam deposition system with substrate entry/exitchamber, buffer chamber and with the possibility to transfer substrate from a III–V molecularbeam deposition system. Flux calibrations of organic molecules and the initial growth oforganic layers are described. For this purpose, the molecules 3,4,9,10 perylene tetra carboxylicdianhydride and copper phtalocyanine were used. Layers were grown on oxidized andhydrogen passivated Si(100), Indium tin oxide and glass respectively. The growth wasinvestigated with atomic force microscopy, reflection high energy electron diffraction andultraviolet photoemission spectroscopy. An investigation with x-ray photoelectron and Ramanspectroscopy on the effect of atmospheric exposure is also included, showing little effect ofsurface pollution when the samples were handled carefully. The initial formation (monolayers)of copper phtalocyanine thin films was studied by ultraviolet photoemission spectroscopy.
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| 3. |
- Adolph, David, 1971, et al.
(författare)
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Plasma-assisted molecular beam epitaxy of ZnO on in-situ grown GaN/4H-SiC buffer layers
- 2015
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Ingår i: Frontiers of Materials Science. - : Springer Science and Business Media LLC. - 2095-025X .- 2095-0268. ; 9:2, s. 185-191
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Tidskriftsartikel (refereegranskat)abstract
- Plasma-assisted molecular beam epitaxy (MBE) was used to grow ZnO (0001) layers on GaN(0001)/4H-SiC buffer layers deposited in the same growth chamber equipped with both N- and O-plasma sources. The GaN buffer layers were grown immediately before initiating the growth of ZnO. Using a substrate temperature of 440 degrees C-445 degrees C and an O-2 flow rate of 2.0-2.5 sccm, we obtained ZnO layers with smooth surfaces having a root-mean-square roughness of 0.3 nm and a peak-to-valley distance of 3 nm shown by AFM. The FWHM for X-ray rocking curves recorded across the ZnO(0002) and ZnO(10 (1) over bar5) reflections were 200 and 950 arcsec, respectively. These values showed that the mosaicity (tilt and twist) of the ZnO film was comparable to corresponding values of the underlying GaN buffer. It was found that a substrate temperature > 450 degrees C and a high Zn-flux always resulted in a rough ZnO surface morphology. Reciprocal space maps showed that the in-plane relaxation of the GaN and ZnO layers was 82.3% and 73.0%, respectively and the relaxation occurred abruptly during the growth. Room-temperature Hall-effect measurements showed that the layers were intrinsically n-type with an electron concentration of 10(19) cm(-3) and a Hall mobility of 50 cm(2).V-1.s(-1).
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| 4. |
- Aggerstam, Thomas, et al.
(författare)
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GaN/AlN multiple quantum well structures grown by MBE on GaN templates for 1.55 mu m intersubband absorption
- 2007
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Ingår i: Quantum Sensing and Nanophotonic Devices IV. - : SPIE. - 9780819465924 ; 6479, s. 64791E-
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Konferensbidrag (refereegranskat)abstract
- We have used MBE to grow MQW structures on MOVPE GaN/sapphire templates. The MQW devices are intended for high speed intersubband electroabsorption modulator devices operating at 1.55-mu m. The GaN/AlN multiple quantum well material was systematically studied regarding the surface morphology, structural characterization and optical property by atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The intersubband resonance energy was also calculated considering many-body effects in n-type doped structures. The multiple quantum well structure showed superior performance in terms of linewidth when grown on GaN templates as compared on sapphire. GaN quantum well and AlN barriers with a thickness of 3.3 and 4.2 nm respectively resulted in FWHM of the intersubband absorption peak as low as 93 meV at an absorption energy of 700 meV. This is promising for intersubband modulator applications.
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| 5. |
- Akabli, H., et al.
(författare)
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Intersubband energies in Al1-yInyN/Ga1-xInxN heterostructures with lattice constant close to aGaN
- 2012
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 52:1, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the conduction band profile and the intersubband transition energy, E-12, of Al1-yInyN/Ga1-xInxN quantum well structures. We have considered how material parameters such as non-parabolicity and the uncertainty in the bowing parameter affect E-12 and the corresponding wavelength, lambda(12). The calculations include strain and cover the transition range from telecommunication wavelengths (1.55 mu m) to the mid-infrared (similar to 10 mu m). Our results show that the transition energies of strain-free Al1-yInyN/Ga1-xInxN quantum well structures, which are lattice-matched to GaN (y = 17.7%, x = 0), resulted in wavelengths above similar to 2 mu m. To reach shorter wavelengths, we explored structures with other indium concentrations but maintaining a small mismatch to GaN. For similar to 1% lattice mismatch the wavelength lambda(12) could be reduced to less than 1.55 mu m. The results serve as a starting point for designing and epitaxial growth of photonic intersubband structures.
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| 6. |
- Amloy, Supaluck, et al.
(författare)
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On the polarized emission from exciton complexes in GaN quantum dots
- 2012
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 100:021901
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Tidskriftsartikel (refereegranskat)abstract
- The optical linear polarization properties of exciton complexes in asymmetric Stranski-Krastanov grown GaN quantum dots have been investigated experimentally and theoretically. It is demonstrated that the polarization angle and the polarization degree can be conveniently employed to associate emission lines in the recorded photoluminescence spectra to a specific dot. The experimental results are in agreement with configuration interaction computations, which predict similar polarization degrees for the exciton and the biexciton (within 10%) in typical GaN quantum dots. The theory further predicts that the polarization degree can provide information about the charge state of the dot.
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| 7. |
- Amloy, Supaluck, et al.
(författare)
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Polarized emission from single GaN quantum dots grown by molecular beam epitaxy
- 2011
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735410022 ; 1399, s. 541-542
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Konferensbidrag (refereegranskat)abstract
- Polarization resolved microphotoluminescence measurements of single MBE-grown GaN/Al(Ga)N quantum dots (QDs) have been performed. The exciton and biexciton peaks with full width at half maximum as narrow as
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| 8. |
- Amloy, Supaluck, et al.
(författare)
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Size dependent biexciton binding energies in GaN quantum dots
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:25
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Tidskriftsartikel (refereegranskat)abstract
- Single GaN/Al(Ga)N quantum dots (QDs) have been investigated by means of microphotoluminescence. Emission spectra related to excitons and biexcitons have been identified by excitation power dependence and polarization resolved spectroscopy. All investigated dots exhibit a strong degree of linear polarization (similar to 90%). The biexciton binding energy scales with the dot size. However, both positive and negative binding energies are found for the studied QDs. These results imply that careful size control of III-Nitride QDs would enable the emission of correlated photons with identical frequencies from the cascade recombination of the biexciton, with potential applications in the area of quantum information processing.
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