| 1. |
- Laukkanen, P., et al.
(författare)
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Formation and destabilization of Ga interstitials in GaAsN : Experiment and theory
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:19, s. 195205-
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Tidskriftsartikel (refereegranskat)abstract
- Using first-principles total energy calculations we have found complex defects induced by N incorporation in GaAsN. The formation energy of the Ga interstitial atom is very significantly decreased due to local effects within the defect complex. The stability of the Ga interstitials is further increased at surfaces. The present results suggest that the energetically favorable Ga interstitial atoms are much more abundant in GaAsN than the previously considered N defects, which have relatively large formation energies. Our synchrotron radiation core-level photoemission measurements support the computational results. The formation of harmful Ga interstitials should be reduced by incorporating large group IV B atoms in GaAsN.
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| 2. |
- Punkkinen, Marko P. J., et al.
(författare)
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Structure of ordered oxide on InAs(100) surface
- 2012
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 606:23-24, s. 1837-1841
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Tidskriftsartikel (refereegranskat)abstract
- It was recently found that oxygen induces ordered reconstructions on several III-V surfaces. The most oxygen-rich reconstruction shows (3x1) periodicity. Based on first-principles investigations, a detailed atomic model is presented for this reconstruction. The uncommon periodicity is attributed to the highly stable In - O - In trilayer below surface which also leads to stabilizing additional bonds within the surface layer. The strain induced by the trilayer is more effectively accommodated within the (3 x 1) reconstruction than within the competing (2 x 1) reconstruction due to smaller number of dimers. It is proposed that the experimentally found semiconductivity is reached by substitutional atoms within the surface layer. Suitable substitution preserves the magnitude of the bulk band gap. (C) 2012 Elsevier B.V. All rights reserved.
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| 3. |
- Metaferia, Wondwosen, et al.
(författare)
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Selective area heteroepitaxy through nanoimprint lithography for large area InP on Si
- 2012
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 9:7, s. 1610-1613
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Tidskriftsartikel (refereegranskat)abstract
- The use of nanoimprint lithography, a low cost and time saving alternative to E-beam lithography, for growing heteroepitaxial indium phosphide layer on silicon is demonstrated. Two types of patterns on 500 nm and 200 nm thick silicon dioxide mask either on InP substrate or InP seed layer on silicon were generated by UV nanoimprint lithography: (i) circular openings of diameter 150 nm and 200 nm and (ii) line openings of width ranging from 200 nm to 500 nm. Selective area growth and epitaxial lateral overgrowth of InP were conducted on these patterns in a low pressure hydride vapour phase epitaxy reactor. The epitaxial layers obtained were characterized by atomic force microscopy, scanning electron microscopy and micro photoluminescence. The growth from the circular openings on InP substrate and InP (seed) on Si substrate is extremely selective with similar growth morphology. The final shape has an octahedral flat top pyramid type geometry. These can be used as templates for growing InP nanostructures on silicon. The grown InP layers from the line openings on InP substrates are ∌ 2.5 Όm thick with root mean square surface roughness as low as 2 nm. Completely coalesced layer of InP over an area of 1.5 mm x 1.5 mm was obtained.The room temperature photoluminescence intensity from InP layers on InP substrate is 55% of that of homoepitaxial InP layer. The decrease in PL intensity with respect to that of the homoepitaxial layer is probably due to defects associated with stacking faults caused by surface roughness of the mask surface. Thus in this study, we have demonstrated that growth of heteroepitaxial InP both homogeneously and selectively on the large area of silicon can be achieved. This opens up the feasibility of growing InP on large area silicon for several photonic applications.
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