| 1. |
- Semchuk, O. Yu., et al.
(författare)
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Thermal effects caused by action of powerful laser radiation on condensed matter
- 2010
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Ingår i: JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS. - : Inoe and Infm. - 1454-4164. ; 12:3, s. 586-588
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Tidskriftsartikel (refereegranskat)abstract
- The spatial and temporal temperature distribution on a solid's surface heated by laser interference pattern is calculated using integral transformation on coordinates x, y and Fourier transformation on coordinate z . Two-dimensional periodic structure consisting of circles with radii equal to a radius of the laser beam is considered. It is shown, that the maximal heating is observed in the center of a circle while diminishing to periphery. The area where the intensive surface heating is observed extends up to 0.8 r/a ( a is a period of the grating, r is a radius of the laser beam).
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| 2. |
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| 3. |
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| 4. |
- Adolfsson, Göran, 1981, et al.
(författare)
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Direct observation of lateral carrier diffusion in ridge waveguide InGaNAs lasers
- 2009
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 21:134, s. 134-136
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Tidskriftsartikel (refereegranskat)abstract
- We present results from measurements of the subthreshold lateral spontaneous emission profile in 1.3-mu m wavelength ridge waveguide InGaNAs quantum-well lasers using a scanning near-field optical microscopy technique. The measurements reveal the presence of significant lateral carrier diffusion which has a profound effect on the temperature dependence of the threshold current. This effect is frequently omitted when the characteristic temperature of the threshold current is considered.
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| 5. |
- Adolfsson, Göran, 1981, et al.
(författare)
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Effects of Lateral Diffusion on the Temperature Sensitivity of the Threshold Current for 1.3 um Double Quantum-Well GaInNAs/GaAs Lasers
- 2008
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Ingår i: IEEE Journal of Quantum Electronics. ; 44:7, s. 607-616
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental and theoretical investigationof the temperature dependence of the threshold current fordouble quantum well GaInNAs–GaAs lasers in the temperaturerange 10 C–110 C. Pulsed measurements of the threshold current have been performed on broad and narrow ridge wave guide(RWG) lasers. The narrow RWG lasers exhibit high characteristic temperatures (T0)of 200 K up to a critical temperature (Tc), above which T0 is reduced by approximately a factor of 2. The T0-values for broad RWG lasers are significantly lower than those for the narrow RWG lasers, with characteristic temperatures on the order of 100 (60) K below (above). Numerical simulations, using a model that accounts for lateral diffusion effects, show good agreement with experimental data and reveal that a weakly temperature dependent lateral diffusion current dominates thethreshold current for narrow RWG lasers.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Baranowski, M, et al.
(författare)
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Contactless Electroreflectance, Photoluminescence and Time-Resolved Photoluminescence of GaInNAs Quantum Wells Obtained by the MBE Method with N-irradiation
- 2011
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 26:4, s. 045012-
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of GaInNAs quantum wells (QW) grown by molecular beam epitaxywith and without N-irradiation (i.e. grown by the classical method) were investigated by thecontactless electroreflectance (CER), temperature-dependent photoluminescence (PL) andtime-resolved PL (TRPL). From CER measurements it was concluded that one type ofnitrogen nearest-neighbor environment (In-rich environment) is dominant for GaInNAs QWsgrown with N-irradiation whereas various nitrogen environments are present for the referenceGaInNAs QW (i.e. the sample obtained by the classical method). PL and TRPL measurementsclearly show that the optical properties of GaInNAs QWs are affected mainly by the amount ofthe incorporated nitride atoms. It was observed that the PL decay time decreased from ∼200to ∼40 ps when the nitrogen concentration is increased from 0.8 to 2.2%. In addition, thepresence of As flux during N-irradiation reduces the amount of the incorporated nitrogen andsimultaneously improves the optical quality of GaInNAs QWs (i.e. it weakens the carrierlocalization at low temperatures and improves the quantum efficiency of PL).
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| 11. |
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| 12. |
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| 13. |
- Dumitrescu, Mihail, et al.
(författare)
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10 Gb/s uncooled dilute nitride optical transmitters operating at 1300 nm
- 2009
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Ingår i: 2009 Conference on Optical Fiber Communication, OFC 2009; San Diego, CA; United States; 22 March 2009 through 26 March 2009. - Washington, D.C. : OSA. - 9781557528650
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Konferensbidrag (refereegranskat)abstract
- Dilute-nitride lasers with record performances have been used to build uncooled transceivers and failure free 10 Gb/s optical transmission was achieved over 815 m of multimode Corning InfiniCor fiber under the LRM standard.
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| 14. |
- Emadi, Arezoo, 1977, et al.
(författare)
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Design, Fabrication and characterisation of High Power HBV Diodes
- 2005
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Ingår i: 16th International Symposium on Space Terahertz Technology; Chalmers Conference Centre, May 2-4, 2005, Gothenburg, Sweden, (Eds. Jan Stake, Harald Merkel.). ; , s. Session: P05-04
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Konferensbidrag (refereegranskat)abstract
- We present design and analysis of material structures and device geometries for heterostructure barrier varactor diodes (HBVs) for high-power frequency multipliers. The methods aim at finding optimum epitaxial layer structures with respect to diode power handling capability and efficiency. A distributed device geometry for further increasing the output power levels whilst maintaining acceptable device temperatures is also presented. Finally, an electro-thermal HBV model with the ability of incorporating temperature-dependent device parameters is used to simulate the introduced devices, followed by a design example of a 3×4-barrier high-power HBV diode.
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| 15. |
- Emadi, Arezoo, 1977, et al.
(författare)
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Optimum Barrier Thickness Study for the Heterostructure Barrier Varactror Diode
- 2006
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Ingår i: WOCSDICE 2006. - 1652-0769. ; , s. 55-57
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Konferensbidrag (refereegranskat)abstract
- This experimental study aims at finding the optimum barrier thickness in heterostructure barrier varactor (HBV) diodes, to improve the diode efficiency especially for high-power frequency multiplier applications. The influence of barrier thickness on the conduction current is investigated for different biases and device temperatures. We found that for an InP-based HBV, there is an optimum barrier thickness range between 10 to 14 nm which causes the lowest possible leakage current.
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| 16. |
- Emadi, Arezoo, 1977, et al.
(författare)
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Optimum barrier thickness study for the InGaAs/InAlAs/AlAs heterostructure barrier varactor diodes
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:1, s. 012108-3
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Tidskriftsartikel (refereegranskat)abstract
- This experimental study aims at finding the optimum barrier thickness in heterostructure barrier varactor (HBV) diodes to improve the diode efficiency especially for high-power frequency multiplier applications. The influence of barrier thickness on the destructive current leaking over and through the barrier is investigated for different biases and operating temperatures. The authors found that for an InP-based HBV, there is an optimum barrier thickness range between 10 to 14 nm which causes the lowest possible leakage current.
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| 17. |
- Fadaly, Elham, et al.
(författare)
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Production of nano-holes patten on Si(111) by colloidal lithography for growth of InAs nanowires
- 2015
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Ingår i: 15th International Conference on Nanotechnology.
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Konferensbidrag (refereegranskat)abstract
- Colloidal lithography is a simple, versatile and low-cost technique that can be used to pattern diverse nanostructures on a wafer scale. In this work, colloidal lithography utilizing polystyrene nanoparticles as a lift-off mask was used to produce nanohole patterns on Si (111) substrates. The hole size, which is determined by the size of the polystyrene particles, can be well controlled by oxygen plasma shrinking. Using this technique, we were able to obtain nanohole pattern with feature size down to 50 nm, which is close to the limit that conventional lithographic techniques can reach, in a time-efficient and cost effective manner. InAs nanowires were successfully grown on the patterned substrates using molecular beam epitaxy.
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| 18. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of a thin GaAs cap layer on structural and optical properties of InAs quantum dots
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:7, s. 1195-7
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Tidskriftsartikel (refereegranskat)abstract
- In this letter we investigate the changes in the surface morphology and emission wavelength of InAs quantum dots (QDs) during initial GaAs encapsulation by atomic force microscopy and photoluminescence. The density (2.9×1010 cm-2) and height (7.9±0.4 nm) of the uncapped QDs decrease and saturate at 0.6×1010 cm-2 and 4 nm, respectively, after the deposition of 4 monolayers (MLs) of GaAs. A model for the evolution of surface morphology is proposed. Photoluminescence spectra of the surface dots show a wavelength shift from 1.58 to 1.22 ?m when the GaAs capping layer thickness increases from 0 to 8 MLs.
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| 19. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of initial GaAs and AlAs cap layers on InAs quantum dots grown by molecular beam epitaxy
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 251:1-4, s. 145-9
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Tidskriftsartikel (refereegranskat)abstract
- Capping of InAs quantum dots (QDs) with AlAs or GaAs causes a significant change in the structural properties of the QDs. However, there is a basic difference between these two capping materials. The GaAs capping causes a dramatic reduction of the dot density and height. AlAs capping, on the other hand, results in a partly suppressed height reduction and a higher dot density.
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| 20. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of thin GaAs and AlAs cap layers on the structural properties of InAs quantum dots grown by molecular beam epitaxy
- 2002
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Ingår i: International Conference on Molecular Beam Epitaxy, 2002. ; , s. 285-6
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Konferensbidrag (refereegranskat)abstract
- Self-organised InAs quantum dots (QDs) are used as optical gain material in long wavelength lasers on GaAs. The measured QD height and density are often used as figures of merits, and great efforts have been made to maximise these two parameters to extend the wavelength coverage. In this work, we investigate the influence of initial GaAs and AlAs cap layers on the structural properties of InAs QDs. The study clearly shows that capping of InAs QDs causes a strong modification of not only the QD shape and height but also the QD density
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| 21. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Optimisation of MBE growth conditions for InAs quantum dots on (001) GaAs for 1.3 μm luminescence
- 2001
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 227-228, s. 1140-5
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the optimised growth conditions for InAs quantum dots (QDs) grown on GaAs substrates by solid source molecular beam epitaxy (SSMBE). Growth conditions for best luminescence intensity and linewidth were found within narrow windows of substrate temperature (500-520°C) and nominal InAs layer thickness (3.3-3.7 monolayers). The emission wavelength of such InAs QDs capped by GaAs was around 1.24 ?m. However, this is redshifted to 1.3 ?m or more by capping the InAs QDs with a thin layer of InxGa1-xAs. The results show that both In content and thickness of the capping layer can be used to tune the emission wavelength. Atomic force microscopy images show that the surface recovers to two-dimensional when depositing In0.2Ga0.8As while remaining three-dimensional when depositing In0.4Ga0.6As.
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| 22. |
- Fu, Ying, et al.
(författare)
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Energy band structure and spectral gain characteristics of dilute-nitride zinc blende InGaNAs quantum wells embedded in GaAs and GaNAs barriers
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 100:7
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Tidskriftsartikel (refereegranskat)abstract
- The spectral gain characteristics of dilute-nitride zinc blende InxGa1-xNyAs1-y quantum wells embedded in GaNy1As1-y1 barriers have been investigated experimentally and theoretically. Two samples, both with the gain peak at 1300 nm, were studied for comparison. One has a high nitrogen concentration in the quantum well with the surrounding barriers being pure GaAs. The other has a lower and uniform nitrogen concentration in the quantum well and the barriers (GaNAs barriers). Measurements show the redshift of the gain peak induced by the incorporation of nitrogen and difference in the spectral gain characteristics. The energy band structures and spectral gain characteristics are analyzed theoretically using the standard eight-band k center dot p theory. It is shown that the introduction of nitrogen atoms in the GaAs barriers reduces the barrier height for the central quantum well so that the energy sublevels in the conduction band becomes condensed. The condensation of the conduction-band energy sublevels reduces the peak gain and makes the gain spectrum narrower, in agreement with measurements.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Khatab, A., et al.
(författare)
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Comparative Optical Studies of InGaAs/GaAs Quantum Wells Grown by MBE on (100) and (311)A GaAs Planes
- 2012
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Ingår i: Physica Status Solidi (C) Current Topics in Solid State Physics. - : Wiley. - 1610-1642 .- 1862-6351. ; 9:7, s. 1621-1623
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the optical properties of InGaAs/GaAs double quantum wells (QWs) grown by molecular beam epitaxy (MBE) on (100) and (311)A GaAs substrates has been studied by photoluminescence (PL). It is found that for an excitation of 50 mW, the PL quenching for (100) and (311)A QWs occurs at 220 K and 300 K, respectively. This suggests that the high index plane (311)A has superior structural properties and less non-radiative defect centers than the conventional (100) plane. The better optical quality of the QWs grown on (311)A is also confirmed by the narrowing of the full width at half-maximum (FWHM) of the PL emission: 10 nm for (311)A and 20 nm for (100). From these findings it is expected that optical devices grown on (311)A GaAs planes should have better performances than those grown on conventional (100) orientation. We have also carried out a systematic study to investigate the effect of post-growth thermal annealing on the optical quality of the QWs. We observed a substantial improvement of the PL efficiency with annealing temperatures in the range 500-700 C for all samples. However, this PL enhancement is accompanied by a blueshift. These energy shifts can be explained by interdiffusion or intermixing of In and Ga atoms at the interfaces between the QWs and the barriers. A noticeable narrowing of the PL linewidth with higher annealing temperatures could be explained by a homogenisation of the quantum well interfaces.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Lim, J.J., et al.
(författare)
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Static and dynamic performance optimization of a 1.3 µm GaInNAs ridge waveguide laser
- 2008
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Ingår i: 2008 International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD'08; Nottingham; United Kingdom; 1 September 2008 through 4 September 2008. - 9781424423071 ; , s. 121-122
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Konferensbidrag (refereegranskat)abstract
- In this work, we optimise the structure of an uncooled directly modulated 1.3 μm GaInNAs ridge waveguide laser for high temperature operation. The static and dynamic performance of the optimised design is analyzed using an accurate in-house 2D electro-opto-thermal laser simulator. The optimised structure Is shown to have a lower threshold current, higher efficiency, higher modulation bandwidth and lower vertical beam divergence compared to a reference structure with a conventional design. Large-signal 10 Gbit/s digital modulation simulations were performed and demonstrate the improved performance of the optimised structure especially under high temperature operation.
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| 33. |
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| 34. |
- Lim, Jun, et al.
(författare)
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Static and dynamic performance optimisation of a 1.3 mu m GaInNAs ridge waveguide laser
- 2008
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Ingår i: Optical and Quantum Electronics. - : Springer Science and Business Media LLC. - 0306-8919 .- 1572-817X. ; 40:14-15, s. 1181-1186
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we perform a multi-parameter design study to improve the performance of an uncooled directly modulated 1.3 mu m GaInNAs ridge waveguide laser for high speed operation especially at high temperature. The static and dynamic performance of the improved design is analyzed using an accurate in-house 2D electro-opto-thermal laser simulator. The improved structure is shown to have a lower threshold current, higher thermal roll-over limit and higher modulation bandwidth-especially under high temperature operation. The improved structure also has a lower vertical beam divergence compared to a reference structure with a conventional design.
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| 35. |
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| 36. |
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| 37. |
- Lopes-Oliveira, V., et al.
(författare)
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Strain and localization effects in InGaAs(N) quantum wells: Tuning the magnetic response
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 116:23
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Tidskriftsartikel (refereegranskat)abstract
- We investigated effects of localization and strain on the optical and magneto-optical properties of diluted nitrogen III-V quantum wells theoretically and experimentally. High-resolution x-ray diffraction, photoluminescence (PL), and magneto-PL measurements under high magnetic fields up to 15 T were performed at low temperatures. Bir-Pikus Hamiltonian formalism was used to study the influence of strain, confinement, and localization effects. The circularly polarized magneto-PL was interpreted considering localization aspects in the valence band ground state. An anomalous behavior of the electron-hole pair magnetic shift was observed at low magnetic fields, ascribed to the increase in the exciton reduced mass due to the negative effective mass of the valence band ground state.
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| 38. |
- Lu, W, et al.
(författare)
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Independent determination of In and N concentrations in GaInNAs alloys
- 2009
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 24:10, s. 105016-
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution x-ray diffraction (HRXRD) and photoreflectance ( PR) spectroscopy were used to independently determine the In and N concentrations in GaInNAs alloys grown by solid-source molecular beam epitaxy (SSMBE). The lattice constant and bandgap energy can be expressed as two independent equations in terms of the In and N concentrations, respectively. The HRXRD measurement provided the lattice constant and the PR measurement extracted the bandgap energy. By simultaneously solving these two equations, we have determined the In and N concentrations with the error as small as 0.001.
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| 39. |
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| 40. |
- Lu, W, et al.
(författare)
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Reliability assessment and degradation analysis of 1.3 µm GaInNAs lasers
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:9, s. 093110-
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Tidskriftsartikel (refereegranskat)abstract
- The degradation of 1.3 mu m GaInNAs lasers was investigated using accelerated aging tests. This was followed by comprehensive characterization, including standard light-current-voltage (L-I-V) characterization, capacitance measurements, photoluminescence microscopy (PLM), on-axis amplified spontaneous emission (ASE) spectra measurements, and photocurrent (PC) and electroluminescence (EL) spectroscopies. The slope efficiency of the device dropped by 50% with a 300% increase in the threshold current after the accelerated aging test. The ideality factors of the aged devices are higher than those of the unaged devices. PLM images showed no evidence of catastrophic optical mirror damage. The measured capacitances of the aged devices are all similar to those of the unaged devices, indicating that there was no significant dopant diffusion in the junction region. Fourier transforms of the ASE spectra showed that no intracavity defects were present in the aged lasers, suggesting that intracavity defects are not responsible for the rapid degradation of the aged devices. Although the PC measurements showed defects at 0.88-0.95 eV and at similar to 0.76 eV, these defect signatures did not increase with aging. On the other hand, EL measurements revealed that radiative deep level defects were generated during the aging tests. which may be related to the degradation of the devices. Based on the above measurement results, we identify, the generation Of radiative deep level defects as the main causes of degradation of these devices.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Risveden, Klas, et al.
(författare)
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Signal frequency studies of an environmental application of a 65 nm region ion sensitive field effect transistor sensor
- 2007
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 127:1, s. 198-203
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Tidskriftsartikel (refereegranskat)abstract
- A rapid and sensitive novel type of bioelectronic Region Ion Sensitive Field Effect Transistor (RISFET) nanosensor was constructed on a chip with a 65 nm sensing electrode gap. The RISFET nanosensor was demonstrated for the environmental pesticide analysis of neurotoxic organocarbamate/carbofuran. The linear range for carbofuran analysis is ac signal frequency dependent, studied in the range (500 down-0.5 Hz, 50 mV(peak-peak) ac) and a bias voltage applied between the bottom capacitor plate and the electrodes. The signal current response is measured using a low-noise pico ammeter. The inhibition of acetylcholinesterase (AChE) by carbofuran was detectable in a logarithmic linear range (0.1-100nM) at 1.08 Hz, with a lower limit of detection of inhibition 0.1 nM with 10 min incubation time. The sensor is based on the principle of focusing charged reaction products with an electrical field in a region between the sensing electrodes. The current measurement by the sensor electrodes is correlated to the composition of the sample. The carbofuran detection is based on the ability to inhibit the enzyme AChE. The RISFET sensor chip is fabricated using conventional electron beam lithography. The encompassed sensor volume in the "nanocell" is in the attoliter range.
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| 48. |
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| 49. |
- Shao, J, et al.
(författare)
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Evolution of Valence-Band Alignment with Nitrogen Content in GaNAs/GaAs Single Quantum Wells
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:3, s. Art. Nr. 031904-
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Tidskriftsartikel (refereegranskat)abstract
- We report on experimental evidence for the transition of valence-band alignment from type I to type II in Ga Nx As1-x GaAs single quantum wells by photoreflectance measurements. The substitutional nitrogen content covers a range of 1.4%-5.9%. The turning point of the type I-type II transition occurs at x4.7%. The experimental observations can be well interpreted by a combination of band anticrossing model and model-solid theory when nonlinear behavior of either the shear deformation potential or the average valence-band energy is taken into account. The effect of dilute nitrogen on the valence-band offset of GaNAsGaAs quantum well structure is hence clarified. © 2008 American Institute of Physics.
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