B. Jenichen - Profile on Academia.edu (original) (raw)
Papers by B. Jenichen
Depth‐resolved measurement of lattice relaxation in Ga1−xInxAs/GaAs strained layer superlattices by means of grazing‐incidence x‐ray diffraction
Journal of Applied Physics, 1993
Applied Physics Letters, 2013
Elastic stress relaxation in GaInAsP quantum wires on InP
Journal of Physics D: Applied Physics, 1999
High resolution x-ray diffractometry and photoluminescence measurements (PL) have been used to co... more High resolution x-ray diffractometry and photoluminescence measurements (PL) have been used to compare the effects of elastic stress relaxation of free standing and overgrown Ga0.22In0.78As0.80P0.20 quantum wire structures on InP. The elastic relaxation occurs near the free surface of the sidewalls resulting only in a minor shift of the PL line. The overgrowth of the structures with a Ga0.22In0.78As0.16P0.84 layer, which has a residual tensile strain of more than 1% compared with the InP substrate, leads to a strong increase of the PL line shift. At the same time, a shift of the x-ray diffraction pattern from the small angle side of the InP peak to the large angle side is observed. In addition, the diffuse scattering increases. The strain fields in the wire structures are calculated, and the diffraction patterns are determined from the strain maps in the kinematical approximation.
Semiconductor Science and Technology, 2019
We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/se... more We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/semiconductor hybrid structures by Volmer–Weber island growth, starting from the epitaxial growth of isolated Fe3Si islands up to the formation of continuous films as a result of island coalescence. We find coherent defect-free layers exhibiting compositional disorder near the Fe3Si/GaAs—interface for higher growth rates, whereas they are fully ordered for lower growth rates.
Investigation of the thickness dependence of the magnetic anisotropy in B2-type Co2TiSi films on ... more Investigation of the thickness dependence of the magnetic anisotropy in B2-type Co2TiSi films on GaAs(001), shows a pronounced perpendicular magnetic anisotropy at 10 K for thicknesses up to 13.5 nm. We have evidenced that the interfacial anisotropy induced by interface clusters has a strong influence on the perpendicular magnetic anisotropy of this hybrid structure, especially at temperatures lower than the blocking temperature of the clusters (28 K). However, as this influence can be ruled out at higher temperatures, the perpendicular magnetic anisotropy which is found to persist up to room-temperature can be ascribed to the magnetic properties of the Co2TiSi films. For thicknesses larger than 15.0 nm, we observe an alignment of the magnetic easy axis parallel to the sample surface, which is most likely due to the shape anisotropy and the film structure.
GaAs/Fe3Si core/shell nanowire structures were fabricated by molecular-beam epitaxy on oxidized S... more GaAs/Fe3Si core/shell nanowire structures were fabricated by molecular-beam epitaxy on oxidized Si(111) substrates and investigated by synchrotron x-ray diffraction. The surfaces of the Fe3Si shells exhibit nanofacets. These facets consist of well pronounced Fe3Si{111} planes. Density functional theory reveals that the Si-terminated Fe3Si{111} surface has the lowest energy in agreement with the experimental findings. We can analyze the x-ray diffuse scattering and diffraction of the ensemble of nanowires avoiding the signal of the substrate and poly-crystalline films located between the wires. Fe3Si nanofacets cause streaks in the x-ray reciprocal space map rotated by an azimuthal angle of 30° compared with those of bare GaAs nanowires. In the corresponding TEM micrograph the facets are revealed only if the incident electron beam is oriented along [1 1 ̄ 0] in accordance with the x-ray results. Additional maxima in the x-ray scans indicate the onset of chemical reactions between Fe3...
Semiconductor Science and Technology, 2018
Journal of Applied Physics, 2016
Co 2 TiSi films were grown by molecular beam epitaxy on GaAs(001) and analyzed using reflection h... more Co 2 TiSi films were grown by molecular beam epitaxy on GaAs(001) and analyzed using reflection high-energy electron diffraction, and electron microscopy. In addition, X-ray diffraction was combined with lattice parameter calculations by density functional theory comparing the L2 1 and B2 structures and considering the influence of non-stoichiometry. Columnar growth is found and attributed to inhomogeneous epitaxial strain from non-random alloying. In films with thicknesses up to 13 nm, these columns may be the origin of perpendicular magnetization with the easy axis perpendicular to the sample surface. We found L2 1 and B2 ordered regions, however the [Co]/[Ti]-ratio is changing in dependence of the position in the film. The resulting columnar structure is leading to anisotropic B2-ordering with the best order parallel to the axes of the columns. Published by AIP Publishing.
Semiconductor Science and Technology, 2006
The structure of epitaxially grown Pr 2 O 3 on Si(0 0 1) has been investigated by grazing inciden... more The structure of epitaxially grown Pr 2 O 3 on Si(0 0 1) has been investigated by grazing incidence x-ray diffraction and x-ray reflectivity. We report experimental results from measurements made in situ, after growth, and during annealing to determine the stability of Pr 2 O 3 at temperatures relevant for complementary metal oxide semiconductor (CMOS) processing. Pr 6 O 11 is evaporated and converted to Pr 2 O 3 using an effusion source operating at 1970 • C. Two different phases of Pr 2 O 3 have been identified in the as-grown films in addition to a silicate layer that forms upon nucleation at the Si interface. The cubic Pr 2 O 3 nucleates as a single crystal and grows in greater proportion to the polycrystalline hexagonal Pr 2 O 3 . The crystal structure of the as-grown film is stable during annealing up to about 800 • C at which point the Pr 2 O 3 is consumed at the expense of the silicate phase.
Physical Review B, 2006
Size effects on a first-order phase transition in submicron disks is demonstrated using a high-re... more Size effects on a first-order phase transition in submicron disks is demonstrated using a high-resolution imaging method. In MnAs disks on GaAs ͑001͒ substrates having sizes smaller than twice the film thickness, an individual disk consists of either entirely ␣-MnAs or entirely -MnAs as a consequence of the nucleation initiation of the first-order phase transition. A phase coexistence occurs on macroscopic scales as the two kinds of the disks can be present simultaneously. In slightly larger disks, the stripe structure due to the phase coexistence in films is modified to a core-shell-type phase segregation.
Physical Review B, 2005
As-grown thin epitaxial Fe 3 Si films fabricated by molecular beam epitaxy on GaAs͑001͒ are studi... more As-grown thin epitaxial Fe 3 Si films fabricated by molecular beam epitaxy on GaAs͑001͒ are studied by grazing incidence x-ray diffraction. The long-range order parameters of the films of different stoichiometry are determined by measuring fundamental and superlattice crystal truncation rods and comparing them to simulations in dynamical approximation. Two order parameters, associated with the degree of migration of Si atoms into different Fe sublattices, are obtained. A residual intermixing of the sublattices is found, even near complete stoichiometry. The relative positions of the Fe 3 Si and GaAs lattices are determined. Fe atoms in Fe 3 Si are located at the positions of the Ga atoms in GaAs, with an additional shift of 0.1± 0.04 Å of the tetragonally distorted Fe 3 Si lattice normal to the interface.
Journal of Crystal Growth, 1999
We report on the structural properties of a series of thin GaN epilayers directly grown on on-axi... more We report on the structural properties of a series of thin GaN epilayers directly grown on on-axis 6H-SiC(0 0 0 1) by plasma-assisted MBE. X-ray measurements show that the crystalline perfection of the layers steadily improves with "lm thickness. In fact, the density of threading defects detected by transmission electron microscopy is found to decrease drastically with the distance away from the GaN/SiC interface, "nally reaching a value of less than 5;10 cm\ at a layer thickness of 0.5 m. The formation mechanisms of the threading dislocations in the GaN "lms are discussed in consideration of the speci"c GaN/SiC interface structure.
Journal of Applied Physics, 2002
d0 magnetism in semiconductors through confining delocalized atomic orbitals Appl. Phys. Lett. 10... more d0 magnetism in semiconductors through confining delocalized atomic orbitals Appl. Phys. Lett. 102, 022422 (2013) Composition and morphology of self-organized Mn-rich nanocolumns embedded in Ge: Correlation with the magnetic properties J. Appl. Phys. 112, 113918 (2012) Depth profile of the tetragonal distortion in thick GaMnAs layers grown on GaAs by Rutherford backscattering/channeling AIP Advances 2, 042102 (2012) Tunable magnetic states in hexagonal boron nitride sheets Appl.
Journal of Applied Physics, 2001
Deformations in heteroepitaxial layer stacks of AlGaAs/GaAs grown on GaAs are measured by triple ... more Deformations in heteroepitaxial layer stacks of AlGaAs/GaAs grown on GaAs are measured by triple crystal diffractometry before epitaxial liftoff and after subsequent wafer bonding on various substrates ͑GaAs, glass, Si, and LiNbO 3 ). The tetragonal deformation present in the as-grown layer stack partially relaxes during epitaxial liftoff. The roughness of the as-grown layer stack gives rise to a bending of the atomic planes after wafer bonding. The widths of the x-ray diffraction peaks are used to estimate the misorientation of the lattice planes and compared with the atomic force microscopy measurements of the surface roughness.
Journal of Applied Physics, 1997
We examined the role of substrate quality on the epitaxial microstructure and performance of pseu... more We examined the role of substrate quality on the epitaxial microstructure and performance of pseudomorphic InGaAs/AlGaAs/GaAs high electron mobility transistors ͑HEMTs͒. High resolution x-ray diffraction, high resolution x-ray topography, and transmission electron microscopy indicate that, for a given channel layer thickness, the misfit dislocation density is always lower for HEMT structures grown on substrates having lower threading dislocation densities. Furthermore, the onset of misfit dislocation formation occurs at higher channel layer thicknesses for HEMTs grown on substrates having a lower threading dislocation density when compared to those grown on substrates with a higher threading dislocation density. However, the ratio of the density of misfit dislocations to threading dislocations is greater than one on the low dislocation density substrates, which demonstrates that other misfit dislocation nucleation sources ͑i.e., surface particulates͒ are significant when there is an insufficient density of threading dislocations. The Hall conductivity measurements show that the performance of HEMT structures improves with higher substrate quality, showing that the range of epitaxial layer metastability increases with improved substrate quality.
Applied Physics Letters, 2002
The effect of the III/V ratio and growth temperature on the In incorporation has been studied in ... more The effect of the III/V ratio and growth temperature on the In incorporation has been studied in thick ͑Ͼ300 nm͒ InGaN layers, with In mole fractions from 19% to 37%, grown by molecular-beam epitaxy on sapphire and on GaN templates. Significant desorption of In occurs at growth temperatures above 550 °C. Symmetric and asymmetric reflections from high resolution X-ray diffraction reveals that the layers are not fully relaxed. A bowing parameter of 3.6 eV is calculated from optical absorption data, once corrected for strain-free band gap values. The increase of both, the absorption band-edge broadening and the photoluminescence full width at half maximum at room temperature with the In content, is discussed in terms of a strong In localization effect. This localization effect is further evidenced by the S-shaped temperature dependence of the emission energy.
Acta Crystallographica Section A Foundations of Crystallography, 2005
Physical Review B, 2003
The structure of phase-separated ͑Ga, Mn͒As, annealed at high temperature (ϳ700°C), is studied by... more The structure of phase-separated ͑Ga, Mn͒As, annealed at high temperature (ϳ700°C), is studied by x-ray diffraction techniques. Analysis of the x-ray diffuse and coherent scattering reveals two types of clusters: ͑1͒ small clusters detected by diffuse scattering through the distortions they produce in the host matrix and ͑2͒ larger clusters with MnAs structure giving rise to coherent diffraction peaks. The average sizes for the two cluster types are estimated to be 5 and 18 nm, respectively. The smaller clusters are found to be of vacancy type. Their density is estimated to be 1.8ϫ10 16 cm Ϫ3. The hexagonal lattice of the larger MnAs crystallites is found to be compressed along the ͓2 110͔ direction by Ϫ0.49% with respect to the bulk hexagonal MnAs lattice. The host zinc blende matrix is found to be under a Ϫ0.20% tensile strain.
Element substitution from substrates in Bi 2 Se 3 , Bi 2 Te 3 and Sb 2 Te 3 overlayers deposited by hot wall epitaxy
Semiconductor Science and Technology, 2014
Investigation of GaAs/AlAs multilayer systems for optical Bragg reflectors using x‐ray double crystal techniques
Journal of Applied Physics, 1993
Depth‐resolved measurement of lattice relaxation in Ga1−xInxAs/GaAs strained layer superlattices by means of grazing‐incidence x‐ray diffraction
Journal of Applied Physics, 1993
Applied Physics Letters, 2013
Elastic stress relaxation in GaInAsP quantum wires on InP
Journal of Physics D: Applied Physics, 1999
High resolution x-ray diffractometry and photoluminescence measurements (PL) have been used to co... more High resolution x-ray diffractometry and photoluminescence measurements (PL) have been used to compare the effects of elastic stress relaxation of free standing and overgrown Ga0.22In0.78As0.80P0.20 quantum wire structures on InP. The elastic relaxation occurs near the free surface of the sidewalls resulting only in a minor shift of the PL line. The overgrowth of the structures with a Ga0.22In0.78As0.16P0.84 layer, which has a residual tensile strain of more than 1% compared with the InP substrate, leads to a strong increase of the PL line shift. At the same time, a shift of the x-ray diffraction pattern from the small angle side of the InP peak to the large angle side is observed. In addition, the diffuse scattering increases. The strain fields in the wire structures are calculated, and the diffraction patterns are determined from the strain maps in the kinematical approximation.
Semiconductor Science and Technology, 2019
We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/se... more We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/semiconductor hybrid structures by Volmer–Weber island growth, starting from the epitaxial growth of isolated Fe3Si islands up to the formation of continuous films as a result of island coalescence. We find coherent defect-free layers exhibiting compositional disorder near the Fe3Si/GaAs—interface for higher growth rates, whereas they are fully ordered for lower growth rates.
Investigation of the thickness dependence of the magnetic anisotropy in B2-type Co2TiSi films on ... more Investigation of the thickness dependence of the magnetic anisotropy in B2-type Co2TiSi films on GaAs(001), shows a pronounced perpendicular magnetic anisotropy at 10 K for thicknesses up to 13.5 nm. We have evidenced that the interfacial anisotropy induced by interface clusters has a strong influence on the perpendicular magnetic anisotropy of this hybrid structure, especially at temperatures lower than the blocking temperature of the clusters (28 K). However, as this influence can be ruled out at higher temperatures, the perpendicular magnetic anisotropy which is found to persist up to room-temperature can be ascribed to the magnetic properties of the Co2TiSi films. For thicknesses larger than 15.0 nm, we observe an alignment of the magnetic easy axis parallel to the sample surface, which is most likely due to the shape anisotropy and the film structure.
GaAs/Fe3Si core/shell nanowire structures were fabricated by molecular-beam epitaxy on oxidized S... more GaAs/Fe3Si core/shell nanowire structures were fabricated by molecular-beam epitaxy on oxidized Si(111) substrates and investigated by synchrotron x-ray diffraction. The surfaces of the Fe3Si shells exhibit nanofacets. These facets consist of well pronounced Fe3Si{111} planes. Density functional theory reveals that the Si-terminated Fe3Si{111} surface has the lowest energy in agreement with the experimental findings. We can analyze the x-ray diffuse scattering and diffraction of the ensemble of nanowires avoiding the signal of the substrate and poly-crystalline films located between the wires. Fe3Si nanofacets cause streaks in the x-ray reciprocal space map rotated by an azimuthal angle of 30° compared with those of bare GaAs nanowires. In the corresponding TEM micrograph the facets are revealed only if the incident electron beam is oriented along [1 1 ̄ 0] in accordance with the x-ray results. Additional maxima in the x-ray scans indicate the onset of chemical reactions between Fe3...
Semiconductor Science and Technology, 2018
Journal of Applied Physics, 2016
Co 2 TiSi films were grown by molecular beam epitaxy on GaAs(001) and analyzed using reflection h... more Co 2 TiSi films were grown by molecular beam epitaxy on GaAs(001) and analyzed using reflection high-energy electron diffraction, and electron microscopy. In addition, X-ray diffraction was combined with lattice parameter calculations by density functional theory comparing the L2 1 and B2 structures and considering the influence of non-stoichiometry. Columnar growth is found and attributed to inhomogeneous epitaxial strain from non-random alloying. In films with thicknesses up to 13 nm, these columns may be the origin of perpendicular magnetization with the easy axis perpendicular to the sample surface. We found L2 1 and B2 ordered regions, however the [Co]/[Ti]-ratio is changing in dependence of the position in the film. The resulting columnar structure is leading to anisotropic B2-ordering with the best order parallel to the axes of the columns. Published by AIP Publishing.
Semiconductor Science and Technology, 2006
The structure of epitaxially grown Pr 2 O 3 on Si(0 0 1) has been investigated by grazing inciden... more The structure of epitaxially grown Pr 2 O 3 on Si(0 0 1) has been investigated by grazing incidence x-ray diffraction and x-ray reflectivity. We report experimental results from measurements made in situ, after growth, and during annealing to determine the stability of Pr 2 O 3 at temperatures relevant for complementary metal oxide semiconductor (CMOS) processing. Pr 6 O 11 is evaporated and converted to Pr 2 O 3 using an effusion source operating at 1970 • C. Two different phases of Pr 2 O 3 have been identified in the as-grown films in addition to a silicate layer that forms upon nucleation at the Si interface. The cubic Pr 2 O 3 nucleates as a single crystal and grows in greater proportion to the polycrystalline hexagonal Pr 2 O 3 . The crystal structure of the as-grown film is stable during annealing up to about 800 • C at which point the Pr 2 O 3 is consumed at the expense of the silicate phase.
Physical Review B, 2006
Size effects on a first-order phase transition in submicron disks is demonstrated using a high-re... more Size effects on a first-order phase transition in submicron disks is demonstrated using a high-resolution imaging method. In MnAs disks on GaAs ͑001͒ substrates having sizes smaller than twice the film thickness, an individual disk consists of either entirely ␣-MnAs or entirely -MnAs as a consequence of the nucleation initiation of the first-order phase transition. A phase coexistence occurs on macroscopic scales as the two kinds of the disks can be present simultaneously. In slightly larger disks, the stripe structure due to the phase coexistence in films is modified to a core-shell-type phase segregation.
Physical Review B, 2005
As-grown thin epitaxial Fe 3 Si films fabricated by molecular beam epitaxy on GaAs͑001͒ are studi... more As-grown thin epitaxial Fe 3 Si films fabricated by molecular beam epitaxy on GaAs͑001͒ are studied by grazing incidence x-ray diffraction. The long-range order parameters of the films of different stoichiometry are determined by measuring fundamental and superlattice crystal truncation rods and comparing them to simulations in dynamical approximation. Two order parameters, associated with the degree of migration of Si atoms into different Fe sublattices, are obtained. A residual intermixing of the sublattices is found, even near complete stoichiometry. The relative positions of the Fe 3 Si and GaAs lattices are determined. Fe atoms in Fe 3 Si are located at the positions of the Ga atoms in GaAs, with an additional shift of 0.1± 0.04 Å of the tetragonally distorted Fe 3 Si lattice normal to the interface.
Journal of Crystal Growth, 1999
We report on the structural properties of a series of thin GaN epilayers directly grown on on-axi... more We report on the structural properties of a series of thin GaN epilayers directly grown on on-axis 6H-SiC(0 0 0 1) by plasma-assisted MBE. X-ray measurements show that the crystalline perfection of the layers steadily improves with "lm thickness. In fact, the density of threading defects detected by transmission electron microscopy is found to decrease drastically with the distance away from the GaN/SiC interface, "nally reaching a value of less than 5;10 cm\ at a layer thickness of 0.5 m. The formation mechanisms of the threading dislocations in the GaN "lms are discussed in consideration of the speci"c GaN/SiC interface structure.
Journal of Applied Physics, 2002
d0 magnetism in semiconductors through confining delocalized atomic orbitals Appl. Phys. Lett. 10... more d0 magnetism in semiconductors through confining delocalized atomic orbitals Appl. Phys. Lett. 102, 022422 (2013) Composition and morphology of self-organized Mn-rich nanocolumns embedded in Ge: Correlation with the magnetic properties J. Appl. Phys. 112, 113918 (2012) Depth profile of the tetragonal distortion in thick GaMnAs layers grown on GaAs by Rutherford backscattering/channeling AIP Advances 2, 042102 (2012) Tunable magnetic states in hexagonal boron nitride sheets Appl.
Journal of Applied Physics, 2001
Deformations in heteroepitaxial layer stacks of AlGaAs/GaAs grown on GaAs are measured by triple ... more Deformations in heteroepitaxial layer stacks of AlGaAs/GaAs grown on GaAs are measured by triple crystal diffractometry before epitaxial liftoff and after subsequent wafer bonding on various substrates ͑GaAs, glass, Si, and LiNbO 3 ). The tetragonal deformation present in the as-grown layer stack partially relaxes during epitaxial liftoff. The roughness of the as-grown layer stack gives rise to a bending of the atomic planes after wafer bonding. The widths of the x-ray diffraction peaks are used to estimate the misorientation of the lattice planes and compared with the atomic force microscopy measurements of the surface roughness.
Journal of Applied Physics, 1997
We examined the role of substrate quality on the epitaxial microstructure and performance of pseu... more We examined the role of substrate quality on the epitaxial microstructure and performance of pseudomorphic InGaAs/AlGaAs/GaAs high electron mobility transistors ͑HEMTs͒. High resolution x-ray diffraction, high resolution x-ray topography, and transmission electron microscopy indicate that, for a given channel layer thickness, the misfit dislocation density is always lower for HEMT structures grown on substrates having lower threading dislocation densities. Furthermore, the onset of misfit dislocation formation occurs at higher channel layer thicknesses for HEMTs grown on substrates having a lower threading dislocation density when compared to those grown on substrates with a higher threading dislocation density. However, the ratio of the density of misfit dislocations to threading dislocations is greater than one on the low dislocation density substrates, which demonstrates that other misfit dislocation nucleation sources ͑i.e., surface particulates͒ are significant when there is an insufficient density of threading dislocations. The Hall conductivity measurements show that the performance of HEMT structures improves with higher substrate quality, showing that the range of epitaxial layer metastability increases with improved substrate quality.
Applied Physics Letters, 2002
The effect of the III/V ratio and growth temperature on the In incorporation has been studied in ... more The effect of the III/V ratio and growth temperature on the In incorporation has been studied in thick ͑Ͼ300 nm͒ InGaN layers, with In mole fractions from 19% to 37%, grown by molecular-beam epitaxy on sapphire and on GaN templates. Significant desorption of In occurs at growth temperatures above 550 °C. Symmetric and asymmetric reflections from high resolution X-ray diffraction reveals that the layers are not fully relaxed. A bowing parameter of 3.6 eV is calculated from optical absorption data, once corrected for strain-free band gap values. The increase of both, the absorption band-edge broadening and the photoluminescence full width at half maximum at room temperature with the In content, is discussed in terms of a strong In localization effect. This localization effect is further evidenced by the S-shaped temperature dependence of the emission energy.
Acta Crystallographica Section A Foundations of Crystallography, 2005
Physical Review B, 2003
The structure of phase-separated ͑Ga, Mn͒As, annealed at high temperature (ϳ700°C), is studied by... more The structure of phase-separated ͑Ga, Mn͒As, annealed at high temperature (ϳ700°C), is studied by x-ray diffraction techniques. Analysis of the x-ray diffuse and coherent scattering reveals two types of clusters: ͑1͒ small clusters detected by diffuse scattering through the distortions they produce in the host matrix and ͑2͒ larger clusters with MnAs structure giving rise to coherent diffraction peaks. The average sizes for the two cluster types are estimated to be 5 and 18 nm, respectively. The smaller clusters are found to be of vacancy type. Their density is estimated to be 1.8ϫ10 16 cm Ϫ3. The hexagonal lattice of the larger MnAs crystallites is found to be compressed along the ͓2 110͔ direction by Ϫ0.49% with respect to the bulk hexagonal MnAs lattice. The host zinc blende matrix is found to be under a Ϫ0.20% tensile strain.
Element substitution from substrates in Bi 2 Se 3 , Bi 2 Te 3 and Sb 2 Te 3 overlayers deposited by hot wall epitaxy
Semiconductor Science and Technology, 2014
Investigation of GaAs/AlAs multilayer systems for optical Bragg reflectors using x‐ray double crystal techniques
Journal of Applied Physics, 1993