| 1. |
- Darakchieva, Vanya, 1971-, et al.
(författare)
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Effects of strain and composition on the lattice parameters and applicability of Vegard's rule in Al-rich Al1-x Inx N films grown on sapphire
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:10, s. 103513-
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Tidskriftsartikel (refereegranskat)abstract
- The lattice parameters and strain evolution in Al1-x In x N films with 0.07≤x≤0.22 grown on GaN-buffered sapphire substrates by metal organic vapor phase epitaxy have been studied by reciprocal space mapping. Decoupling of compositional effects on the strain determination was accomplished by measuring the In contents in the films both by Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD). Differences between XRD and RBS In contents are discussed in terms of compositions and biaxial strain in the films. It is suggested that strain plays an important role for the observed deviation from Vegard's rule in the case of pseudomorphic films. On the other hand, a good agreement between the In contents determined by XRD and RBS is found for Al1-x Inx N films with low degree of strain or partially relaxed, suggesting applicability of Vegard's rule in the narrow compositional range around the lattice matching to GaN. © 2008 American Institute of Physics.
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| 2. |
- Darakchieva, Vanya, et al.
(författare)
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Free electron properties and hydrogen in InN grown by MOVPE
- 2011
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Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : WILEY-BLACKWELL, COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA. - 1862-6300. ; 208:5, s. 1179-1182
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a comprehensive study on the hydrogen impurities, free electron, and structural properties of MOVPE InN films with state-of-the-art quality. We find a correlation between the decrease of free electron concentration and the reduction of bulk hydrogen in the films upon thermal annealing, while no changes in the dislocation densities and strain are observed. Our results suggest that hydrogen is a major source for the unintentional n-type doping in MOVPE InN.
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| 3. |
- Darakchieva, Vanya, et al.
(författare)
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Lattice parameters, deviations from Vegards rule, and E-2 phonons in InAlN
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:26, s. 261908-
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Tidskriftsartikel (refereegranskat)abstract
- The lattice parameters of InxAl1-xN in the whole compositional range are studied using first-principle calculations. Deviations from Vegards rule are obtained via the bowing parameters, delta(a)=0.0412 +/- 0.0039 A and delta(c)=-0.060 +/- 0.010 A, which largely differ from previously reported values. Implications of the observed deviations from Vegards rule on the In content extracted from x-ray diffraction are discussed. We also combine these results with x-ray diffraction and Raman scattering studies on InxAl1-xN nanocolumns with 0.627 <= x <= 1 and determine the E-2 phonon frequencies versus In composition in the scarcely studied In-rich compositional range.
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| 4. |
- Darakchieva, Vanya, et al.
(författare)
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Role of impurities and dislocations for the unintentional n-type conductivity in InN
- 2009
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Ingår i: PHYSICA B-CONDENSED MATTER. - : Elsevier BV. - 0921-4526. ; 404:22, s. 4476-4481
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Tidskriftsartikel (refereegranskat)abstract
- We present a study on the role of dislocations and impurities for the unintentional n-type conductivity in high-quality InN grown by molecular beam epitaxy. The dislocation densities and H profiles in films with free electron concentrations in the low 10(17) cm(-1) and mid 10(18) cm(-3) range are measured, and analyzed in a comparative manner. It is shown that dislocations alone could not account for the free electron behavior in the InN films. On the other hand, large concentrations of H sufficient to explain, but exceeding substantially, the observed free electron densities are found. Furthermore, enhanced concentrations of H are revealed at the film surfaces, resembling the free electron behavior with surface electron accumulation. The low-conductive film was found to contain C and it is suggested that C passivates the H donors or acts as an acceptor, producing compensated material in this case. Therefore, it is concluded that the unintentional impurities play an important role for the unintentional n-type conductivity in InN. We suggest a scenario of H incorporation in InN that may reconcile the previously reported observations for the different role of impurities and dislocations for the unintentional n-type conductivity in InN.
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| 5. |
- Darakchieva, Vanya, 1971-, et al.
(författare)
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Strain and compositional analyzes of Al-rich Al1-xInxN alloys grown by MOVPE : impact on the applicability of Vegard's rule
- 2008
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Ingår i: Physica Status Solidi (C) Current Topics in Solid State Physics. - : Wiley. ; , s. 1859-1862
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Konferensbidrag (refereegranskat)abstract
- We have studied composition and strain in Al1–xInxN films with 0.128≤ x≤ 0.22 grown on GaN-buffered sapphire substrates by metalorganic vapor phase epitaxy. A good agreement between the In contents determined by Rutherford backscattering spectrometry (RBS) and Xray diffraction (XRD) is found for x≤ 18, suggesting applicability of Vegard's rule in the narrow compositional range around the lattice matching to GaN. The increase of the In content up to x = 0.22 leads to a formation of sub-layers with a higher composition, accompanied by deviations from Vegard's rule. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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| 6. |
- Darakchieva, Vanya, et al.
(författare)
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Structural anisotropy of nonpolar and semipolar InN epitaxial layers
- 2010
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Ingår i: JOURNAL OF APPLIED PHYSICS. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 108:7, s. 073529-
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) gamma-LiAlO2, respectively, and semipolar (10 (1) over bar1) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111) A and InN(111) B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices.
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| 7. |
- Darakchieva, Vanya, et al.
(författare)
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Unintentional incorporation of H and related structural and free-electron properties of c- and a-plane InN
- 2012
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Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : Wiley-VCH Verlag Berlin. - 1862-6300. ; 209:1, s. 91-94
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a comprehensive study on the hydrogen impurity depth profiles in InN films with polar c-plane and nonpolar a-plane surface orientations in relation to their structural and free-electron properties. We find that the as-grown nonpolar films exhibit generally higher bulk and near-surface H concentrations compared to the polar InN counter-parts. The latter may be partly associated with a change in the growth mode from 2D to 3D and a decrease in the grain size. Thermal annealing leads to a reduction of H concentrations and the intrinsic H levels are influenced by the structural characteristics of the films. The factors allowing reduction of bulk H and free electron concentrations in a-plane films are discussed.
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| 8. |
- Darakchieva, Vanya, et al.
(författare)
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Unintentional incorporation of hydrogen in wurtzite InN with different surface orientations
- 2011
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 110:6, s. 063535-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 (1) over bar) to (1 (1) over bar 01) and to (11 (2) over bar0), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 degrees C in N(2) leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films.
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| 9. |
- Darakchieva, Vanya, et al.
(författare)
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Unravelling the free electron behavior in InN
- 2008
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Ingår i: Optoelectronic and Microelectronic Materials and Devices, 2008. - : IEEE. - 9781424427161 ; , s. 90-97
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Konferensbidrag (refereegranskat)abstract
- Precise measurement of the optical Hall effect in InN using magneto-optical generalized ellipsometry at IR and THz wavelengths, allows us to decouple the surface accumulation and bulk electron densities in InN films by non-contact optical means and further to precisely measure the effective mass and mobilities for polarizations parallel and perpendicular to the optical axis. Studies of InN films with different thicknesses, free electron densities and surface orientations enable an intricate picture of InN free electron properties to emerge. Striking findings on the scaling factors of the bulk electron densities with film thickness further supported by transmission electron microscopy point to an additional thickness dependent doping mechanism unrelated to dislocations. Surface electron accumulation is observed to occur not only at polar but also at non-polar and semi-polar wurtzite InN, and zinc blende InN surfaces. The persistent surface electron density shows a complex behavior with bulk density and surface orientation. This behavior might be exploited for tuning the surface charge in InN.
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| 10. |
- Olsson, Fredrik, et al.
(författare)
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Epitaxial lateral overgrowth of InP in micro line and submicro mesh openings
- 2007
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Ingår i: 2007 International Conference on Indium Phosphide and Related Materials. ; , s. 311-314
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Konferensbidrag (refereegranskat)abstract
- Towards achieving a large area of InP on silicon, a study of ELOG of InP on InP has been undertaken on lines with different orientations and with openings that are 100 mu m long and 10 gm wide. This knowledge has been transposed on sub-micro mesh structures. By this method we have obtained 2 gm thick InP on a mesh patterned InP. The layer exhibits room temperature photoluminescence (PL) with a full width half maximum of 24 nm. We propose that this intensity can be increased if nano-sized openings are used.
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| 11. |
- Olsson, Fredrik, et al.
(författare)
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Epitaxial lateral overgrowth of InP on Si from nano-openings : Theoretical and experemintal indication for defect filtering throughout the grown layer
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 104:9, s. 093112-1-093112-6
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Tidskriftsartikel (refereegranskat)abstract
- We present a model for the filtration of dislocations inside the seed window in epitaxial lateral overgrowth (ELO). We found that, when the additive effects of image and gliding forces exceed the defect line tension force, filtering can occur even in the openings. The model is applied to ELO of InP on Si where the opening size and the thermal stress arising due to the mask and the grown material are taken into account and analyzed. Further, we have also designed the mask patterns in net structures, where the tilting angles of the openings in the nets are chosen in order to take advantage of the filtering in the openings more effectively, and to minimize new defects due to coalescence in the ELO. Photoluminescence intensities of ELO InP on Si and on InP are compared and found to be in qualitative agreement with the model.
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| 12. |
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| 13. |
- Palisaitis, Justinas, et al.
(författare)
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Standard-free composition measurements of Alx In1–xN by low-loss electron energy loss spectroscopy
- 2011
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Ingår i: physica status solidi (RRL) – Rapid Research Letters. - : Wiley. - 1862-6270 .- 1862-6254. ; 5:2, s. 50-52
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a standard-free method to retrieve compositional information in Alx In1–xN thin films by measuring the bulk plasmon energy (Ep), employing electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Two series of samples were grown by magnetron sputter epitaxy (MSE) and metal organic vapor phase epitaxy (MOVPE), which together cover the full com- positional range 0 ≤ x ≤ 1. Complementary compositional measurements were obtained using Rutherford backscattering spectroscopy (RBS) and the lattice parameters were obtained by X-ray diffraction (XRD). It is shown that Ep follows a linear relation with respect to composition and lattice parameter between the alloying elements from AlN to InN allowing for straightforward compositional analysis.
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| 14. |
- Xie, Jiaying, et al.
(författare)
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STING activation in TET2-mutated hematopoietic stem/progenitor cells contributes to the increased self-renewal and neoplastic transformation
- 2023
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Ingår i: Leukemia. - : Springer Nature. - 0887-6924 .- 1476-5551. ; 37:12, s. 2457-2467
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Tidskriftsartikel (refereegranskat)abstract
- Somatic loss-of-function mutations of the dioxygenase Ten-eleven translocation-2 (TET2) occur frequently in individuals with clonal hematopoiesis (CH) and acute myeloid leukemia (AML). These common hematopoietic disorders can be recapitulated in mouse models. However, the underlying mechanisms by which the deficiency in TET2 promotes these disorders remain unclear. Here we show that the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway is activated to mediate the effect of TET2 deficiency in dysregulated hematopoiesis in mouse models. DNA damage arising in Tet2-deficient hematopoietic stem/progenitor cells (HSPCs) leads to activation of the cGAS-STING pathway which in turn promotes the enhanced self-renewal and development of CH. Notably, both pharmacological inhibition and genetic deletion of STING suppresses Tet2 mutation-induced aberrant hematopoiesis. In patient-derived xenograft (PDX) models, STING inhibition specifically attenuates the proliferation of leukemia cells from TET2-mutated individuals. These observations suggest that the development of CH associated with TET2 mutations is powered through chronic inflammation dependent on the activated cGAS-STING pathway and that STING may represent a potential target for intervention of relevant hematopoietic diseases.
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| 15. |
- Xie, Mengyao, et al.
(författare)
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Assessing structural, free-charge carrier, and phonon properties of mixed-phase epitaxial films: The case of InN
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 90:19, s. 195306-
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Tidskriftsartikel (refereegranskat)abstract
- We develop and discuss appropriate methods based on x-ray diffraction and generalized infrared spectroscopic ellipsometry to identify wurtizte and zinc-blende polymorphs, and quantify their volume fractions in mixed-phase epitaxial films taking InN as an example. The spectral signatures occurring in the azimuth polarization (Muller matrix) maps of mixed-phase epitaxial InN films are discussed and explained in view of polymorphism (zinc-blende versus wurtzite), volume fraction of different polymorphs and their crystallographic orientation, and azimuth angle. A comprehensive study of the structural, phonon and free electron properties of zinc-blende InN films containing inclusions of wurtzite InN is also presented. Thorough analysis on the formation of the zinc-blende and wurtzite phases is given and the structural evolution with film thickness is discussed in detail. The phonon properties of the two phases are determined and discussed together with the determination of the bulk free-charge carrier concentration, and electron accumulation at the mixed-phase InN film surfaces.
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| 16. |
- Xie, Mengyao, et al.
(författare)
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Effect of impurities on the lattice parameters of InN
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We study the effect of the most common impurities and dopants on the lattice parameters of InN by using ab-initio calculations. We have considered both the size and deformation potential effect and report results for H, O, Si andMg. The incorporation of H on interstitial site and substitutional O leads to expansion of the lattice. On the other hand, incorporation of Si or Mg leads to contraction of the lattice. The most pronounced effect is observed for Si. Our results indicate that the increase of the in-plane lattice parameter of Mg doped InN cannot be explained neither by the size nor by the deformation potential effect and suggest that the growth strain is changed in this case.a)Electronic mail: vanya@ifm.liu.se.
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| 17. |
- Xie, Mengyao, et al.
(författare)
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Effect of Mg doping on the structural and free-charge carrier properties of InN
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:16, s. 163504-
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Tidskriftsartikel (refereegranskat)abstract
- We study the structural and free-charge carrier properties of two sets of InN films grown by molecular beam epitaxy doped with different Mg concentrations from 1x1018 cm-3 to 3.9x1021 cm-3. We determine the effect of Mg doping on surface morphology, lattice parameters, structural characteristics and carrier properties. We show that infrared spectroscopic ellipsometry can be used to evidence successful p-type doping in InN, which is an important issue in InN. High resolution X-ray diffraction, combined with atomic force microscopy measurements reveals a drastic decrease in structural quality of the film for Mg concentrations above 1020 cm-3, accompanied with a significant increase in surface roughness. In addition, a decrease of the c-lattice parameter and an increase of the a-lattice parameter are found with increasing Mg concentration. Different contributions to the strain are discussed and it is suggested that the incorporation of Mg leads to a change of growth mode and generation of tensile growth strain. At high Mg concentrations zinc-blende InN inclusions appear which are suggested to originate from higher densities of stacking faults. Infrared spectroscopic ellipsometry analysis shows a reduced LPP-coupling, manifested as a characteristic dip in the IRSE data, and qualitatively different broadening behavior for Mg concentrations between 1.1x1018 cm−3 and 2.9x1019 cm−3 indicate the existence of a p-type conducting bulk InN layer for these Mg concentrations.
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| 18. |
- Xie, Mengyao, et al.
(författare)
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Elastic constants, composition, and piezolectric polarization in InxAl1-xN: From ab initio calculations to experimental implications for the applicability of Vegards rule
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 86:15, s. 155310-
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical analysis on the applicability of Vegards linear rule in InxAl1-xN alloys in relation to strain related elastic and piezoelectric properties. We derive the elastic stiffness constants and biaxial coefficients, as well as the respective deviations from linearity (Vegards rule) by using ab initio calculations. The stress-strain relationships to extract composition from the lattice parameters are derived in different coordinate systems for InxAl1-xN with an arbitrary surface orientation. The error made in the composition extracted from the lattice parameters if the deviations from linearity are not taken into account is discussed for different surface orientations, compositions and degrees of strain in the InxAl1-xN films. The strain induced piezoelectric polarization is analyzed for InxAl1-xN alloys grown pseudomorphically on GaN. The polarization values are compared with those obtained from our experimental data for the lattice parameters. We establish the importance of the deviation from linearity to correctly determine the piezoelectric polarization and also a smooth, not particular piezoelectric response at GaN lattice matched conditions.
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| 19. |
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| 20. |
- Xie, Mengyao, 1982-
(författare)
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Structural and elastic properties of InN and InAlN with different surface orientations and doping
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Group–III nitrides, InN, GaN, AlN, and their alloys, have revolutionized solid state lighting and continue to attract substantial research interest due to their unique properties and importance for optoelectronics and electronics. Among the group–III nitrides, InN has the lowest effective electron mass and the highest electron mobility, which makes it suitable for high–frequency and high power devices. InxAl1–xN alloys cover the widest wavelength region among any semiconductor systems with band gaps ranging from 0.6 eV (InN) to 6.2 eV (AlN). Thus, InxAl1–xN is promising for light emitting diodes and laser diodes in a wide spectral range from infrared to deep ultraviolet, as well as for solar cell applications. InxAl1–xN thin films are also extensively studied in relation to their application for Bragg reflectors, microcavities, polariton emission and high electron mobility transistors. Despite the intense research, many of the fundamental properties of InN and InxAl1–xN remain controversial. For example, the material lattice parameters, stiffness constants, structural anisotropy and defects in nonpolar and semipolar films, effect of impurities and dopants are not established. Furthermore, to fabricate InN based devices, reliable n– and p–type doping should be achieved. At present, control and assessment of p–type conductivity using Mg doping of InN is one of the most outstanding issues in the field.This thesis focuses on: i) Establishing the structural and elastic properties of InxAl1−xN with arbitrary surface orientations (papers I to III); ii) Studying structural and free-charge carrier properties of non/semi-polar and zinc-blende InN (papers IV and V) and iii) Establishing the effects of doping (p and n) on lattice parameters, structural and free-charge carrier properties of InN (Papers VI and VII). The work includes ab initio calculations and experimental studies of InN and InxAl1−xN materials grown in world−class laboratories in Japan, Europe and the USA.The first part of the thesis includes general description of the basic material properties. Next, the structural and elastic properties and defects in InxAl1−xN and InN are discussed. The experimental techniques and relevant methods used to characterize the materials are described, as well as details on the ab initio calculations used in this work are provided. Part II consists ofseven papers.In Paper I we present the first theoretical analysis on the applicability of Vegard’s linear rule in InxAl1−xN alloys in relation to strain related elastic and piezoelectric properties. We derive the elastic stiffness constants and biaxial coefficients, as well as the respective deviations from linearity by using ab initio calculations. The stress−strain relationships to extract composition from the lattice parameters are derived in different coordinate systems for InxAl1−xN with an arbitrary surface orientation. The error made in the composition extracted from the lattice parameters if the deviations from linearity are not taken into account is discussed for different surface orientations, compositions and degrees of strain. The strain induced piezoelectric polarization is analyzed for InxAl1−xN alloys grown psudomorphically on GaN. We establish the importance of the deviation from linearity in the extracted strain values in respect to the piezoelectric polarization.Paper II reports the lattice parameters of InxAl1−xN in the whole compositional range using first-principle calculations. Deviations from Vegard’s rule are obtained via the bowing parameters, which largely differ from previously reported values. The paper discusses for the first time the implications of the observed deviations from Vegard’s rule on the In content extracted from x-ray diffraction.Paper III discusses the lattice parameters and strain evolution in Al−rich InxAl1−xN films with composition. Decoupling of compositional effects on the strain determination was accomplished by measuring the In contents in the films both by Rutherford backscattering spectrometry (RBS) and x−ray diffraction (XRD). It is suggested that strain plays an important role for the observed deviation from Vegard’s rule in the case of pseudomorphic films. It is found that Vegard’s rule in the narrow compositional range around the lattice matching to GaN may be applicable.Paper IV reports the first study of structural anisotropy of non-polar InN and semi−polar InN grown on sapphire and γ-LiAlO2 substrates. The on−axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a−plane InN films is suggested. The semipolar InN was found to contain two domains nucleating on zinc−blende InN(111)A and InN(111)B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. We found that a− and m−plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free−standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN−based devices.Paper V reports the development of appropriate methods based on X-ray diffraction and Infrared spectroscopic ellipsometry to identify wurtizte and zinc-blende InN and quantify their phase ratio. Detailed analysis on the formation of the cubic and wurtzite phases is presented and their evolution with film thickness is discussed in detail. The free-charge carrier and phonon properties of the two phases are discussed together with the determination of the surface electron accumulation.Paper VI studies the effect of Mg doping on the structural parameters and free−charge carrier properties of InN. We demonstrate the capability of infrared spectroscopic ellipsometry to identify p−type doping. The paper provides important information on the effect of Mg doping on extended defects and lattice parameters, and also discussed the relationship between doping, defects and carrier mobility.Paper VII presents the first study on the effect of impurities on the lattice parameters of InN using first principle calculations. We considered both the size and the deformation potential effect for Mg0, Mg−, Si+ and O+ and Hi+. The incorporation of H on interstitial site and substitutional O leads to expansion of the lattice. On the other hand, incorporation of Si or Mg leads to contraction of the lattice. The most pronounced effect is observed for Si. Our results indicate that the experimentally observed increase of the in−plane lattice parameter of Mg doped InN cannot be explained neither by the size nor by the deformation potential effect and suggest that the growth strain is changed in this case. The reported size and deformation potential coefficients can be used to elucidate the origin of strains in InN epitaxial layers and the degree of electrically active impurities.
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| 21. |
- Xie, Mengyao, et al.
(författare)
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Structural, free-charge carrier and phonon properties of zinc-blende and wurtizte polymorphs in InN epitaxial layers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present a comprehensive study of the structural, phonon and free electron properties of zincblende InN films containing inclusion of wurtzite InN. Appropriate methods based on X-ray diffraction and Infrared spectroscopic ellipsometry to identify wurtizte and zinc-blende InN and quantify their phase ratio are developed and discussed. Thorough analysis on the formation of the cubic and wurtzite phases is presented and their evolution with film thickness is discussed in detail. The freecharge carrier and phonon properties of the two phases are discussed together with the determination of electron accumulation at the zinc-blende InN (001) and wurtzite (10̅11) surfaces.
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