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- Song, Yuxin, 1981, et al.
(författare)
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Effects of doping and grading slope on surface and structure of metamorphic InGaAs buffers on GaAs substrates
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:12, s. 123531-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effects of doping and grading slope on the surface and structure of linearly alloy graded InGaAs buffers. It is found that the Be doping can improve material properties, resulting in smaller surface roughness and a lower threading dislocation density, while the Si doping has an opposite effect. The effect is strongly dependent on the grading slope. A moderate In grading slope is preferable for the strain relaxation and the minimization of the negative effect of Si doping. Physical mechanisms are proposed to explain the experimental observations. Since doping is essential for many types of optoelectronic devices, these results are valuable for improving the material properties and performance of metamorphic devices.
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- Tångring, Ivar, 1978, et al.
(författare)
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1.58 µm InGaAs quantum well laser on GaAs
- 2007
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Ingår i: Applied Physics Letters. ; 91, s. 221101-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the 1.58 µm emission at room temperature from a metamorphic In0.6Ga0.4As quantum well laser grown on GaAs by molecular beam epitaxy. The large lattice mismatch was accommodated through growth of a linearly graded buffer layer to create a high quality virtual In0.32Ga0.68As substrate. Careful growth optimization ensured good optical and structural qualities. For a 1250×50 µm2 broad area laser, a minimum threshold current density of 490 A/cm2 was achieved under pulsed operation. This result indicates that metamorphic InGaAs quantum wells can be an alternative approach for 1.55 µm GaAs-based lasers.
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| 5. |
- Tångring, Ivar, 1978, et al.
(författare)
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A study of the doping influence on strain relaxation of graded composition InGaAs layers grown by molecular beam epitaxy
- 2009
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 311, s. 1684-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the role of p- and n-type doping in strain relaxation of graded composition InGaAs layers grown by molecular beam epitaxy. It is found that p-type Be-doping can improve material properties, resulting in smaller surface roughness and lower threading dislocation density, while n-type Si-doping has an opposite effect. The effect is strongly dependent on the grading profile, with linear grading showing small differences, while there is a significant difference when an exponential grading is used. Since doping is essential for many types of devices, these results are useful for improving the material properties and performance of metamorphic devices.
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| 6. |
- Tångring, Ivar, 1978
(författare)
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Design and Characterization of 1.3-1.6 µm Metamorphic Materials and Lasers on GaAs
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of fiber-optical networks for broad-band access is expected to create a huge market for laser transmitters in the 1.3-1.55 µm wavelength range. The existing InP-based lasers have poor temperature stability. GaAs-based lasers can have better thermal properties due to larger conduction band offset in the quantum well (QW) and as a further advantage they are compatible with the highlyreflective AlAs/GaAs distributed Bragg reflectors (DBRs) used in vertical-cavity surface-emitting lasers (VCSELs). However, in order to achieve lasing wavelengths longer than 1.2-1.25 µm on GaAs traditionally either highly strained GaInNAsQWs or InAs quantum dots (QDs) have been used. In this work we investigate a different scheme to realize 1-3-1.55 µm emission on GaAs, the metamorphic technique. Metamorphic growth is a method for producing semiconductor heterostructures on a virtual substrate with a desired lattice constant.We use an alloy graded InGaAs buffer layer to bridge the gap between the GaAs substrate and the virtual substrate, and focus on optimization of buffer layer design and epitaxial growth parameters. The graded buffer layers show typical cross-hatch surface morphologies with minimum root-mean-square roughness as low as 1.1 nm for In[0.25]Ga[0.75]As, providing smooth, relaxed templates for growth of devices. We demonstrate that it is possible to achieve strong light emission from InGaAs QWs on GaAs wafers in the broad wavelength range of 1.25-1.61 µm. We successfully demonstrate the first 4µmwide ridge waveguide lasers operating at 1.25-1.285 µm wavelength under pulsed condition. The minimum threshold current is 60 mA for a 1.5 mm long cavity and maximum slope efficiency is 18 %. Pulsed lasing can be sustained for a maximum duty-cycle of 80 %.
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| 10. |
- Tångring, Ivar, 1978, et al.
(författare)
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Manipulation of strain relaxation in metamorphic heterostructures
- 2007
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Ingår i: Applied Physics Letters. ; 90, s. 071904-
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Tidskriftsartikel (refereegranskat)abstract
- The authors have discovered that high doping densities in an alloy graded InGaAs buffer havedramatic effects on strain relaxation dynamics and consequently surface and optical qualities inmetamorphic heterostructures. Compared with undoped graded buffers, the use of Be dopingsignificantly improves structural, surface, and optical qualities while the use of Si dopingdeteriorates all these properties. This discovery is significant for the realization of metamorphicoptoelectronic devices.
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