The Experts below are selected from a list of 19428 Experts worldwide ranked by ideXlab platform
J M Hartmann - One of the best experts on this subject based on the ideXlab platform.
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impact of strain and Ge Concentration on the performance of planar siGe band to band tunneling transistors
Solid-state Electronics, 2012Co-Authors: M Schmidt, J M Hartmann, R A Minamisawa, S Richter, R Luptak, D Buca, Qingtai Zhao, S MantlAbstract:Abstract Compressively strained Si1−xGex band-to-band tunneling field effect transistors (TFETs) with planar structure are fabricated and analyzed. Different Germanium Concentrations of x = 0.35, 0.50 and 0.65 are investigated. An HfO2/TiN high-κ/metal gate stack is used for a better electrostatic control. The fabricated Si0.5Ge0.5 devices show the highest on-state current Ion and the smallest subthreshold slope (4 μA/μm and 162 mV/dec, respectively), whereas the performance of Si0.35Ge0.65 TFETs is degraded due to partial strain relaxation. The influences of Ge content and elastic strain, via band gap narrowing and effective mass chanGe on the band to band tunneling effect are discussed. Simulations using a nonlocal band-to-band-tunneling model indicate that the transistor performance is enhanced with increasing Ge content and strain, in agreement with our experimental results.
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impact of strain and Ge Concentration on the performance of planar siGe band to band tunneling transistors
International Conference on Ultimate Integration on Silicon, 2011Co-Authors: M Schmidt, J M Hartmann, R A Minamisawa, S Richter, R Luptak, D Buca, Qingtai Zhao, A T Tiedemann, S MantlAbstract:Compressively strained Si 1−x Ge x band-to-band tunneling field effect transistors with planar structure and HfO 2 /TiN gate stack have been produced and analyzed, with different Germanium Concentrations of x = 0.35, 0.50 and 0.65. Simulations using a nonlocal band-to-band-tunneling model have been carried out to understand the switching behavior and its dependence on the material parameters. One would expect an increase of the tunneling currents for the increase of x. However, the Si 0.5 Ge 0.5 devices show the highest I on and smallest S, whereas Si 0.35 Ge 0.65 devices exhibit decreased currents due to partial strain relaxation.
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siGe virtual substrates growth up to 50 Ge Concentration for si Ge dual channel epitaxy
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2005Co-Authors: Y Bogumilowicz, J M Hartmann, Nikolay Cherkashin, A Claverie, G Rolland, T BillonAbstract:Abstract We have grown in reduced pressure–chemical vapor deposition (RP-CVD) SiGe virtual substrates with Ge Concentrations ranging from 20 up to 50%. We have observed an increase of the surface rms roughness with the final Ge content of the virtual substrates. Cross sectional transmission electron microscopy imaGes revealed an effective confinement of the misfit dislocations inside the graded buffer. The final Ge content of the virtual substrate has no impact on the field threading dislocations density, whereas an increase of the pile-up threading dislocations density occurred. We have then used Si0.49Ge0.51 virtual substrates as templates for the growth of Si/Ge dual channels. Although some dislocations were observed, mainly in the silicon layer, we have demonstrated the growth feasibility of such highly mismatched heterostructures in RP-CVD.
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reduced pressure chemical vapour deposition of siGe virtual substrates for high mobility devices
Semiconductor Science and Technology, 2004Co-Authors: J M Hartmann, Y Bogumilowicz, G Rolland, P Holliger, F Laugier, R Truche, M N Semeria, V Renard, E B OlshanetskyAbstract:We have studied the strain state, film and surface morphology of SiGe virtual substrates grown by reduced pressure chemical vapour deposition (RP-CVD). The macroscopic strain relaxation and the Ge composition of those virtual substrates have been estimated in high resolution x-ray diffraction, using Omega-2Theta scans around the (004) and (224) orders. Typically, linearly graded Si0.7Ge0.3 virtual substrates 5 ?m thick are 96% relaxed. From transmission electron microscopy, we confirm that the misfit dislocations Generated to relax the lattice mismatch between Si and SiGe are mostly confined inside the graded layer. The threading dislocations density obtained for Ge Concentrations of 20% and 27% is indeed typically of the order of (7.5 ? 2.5) ?105 cm?2. The surface roughness of the relaxed SiGe virtual substrates increases significantly as the Ge Concentration approaches 30%. We find for the technologically important Ge Concentration of 30% a surface root mean square roughness of 5 nm, with an undulation wavelength for the cross-hatch of the order of 1 ?m. We have also studied the electronic quality of our RP-CVD grown SiGe virtual substrates. We have grown a MODFET-like heterostructure for this purpose, with a buried tensile-strained Si channel 8 nm thick embedded inside SiGe 31%. We have obtained a well-behaved two-dimensional electron gas in the Si channel, with electron sheet densities and mobilities at 1.45 K of 5.7 ? 1011 cm?2 and 180?000 cm2 V?1 s?1, respectively.
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gas source molecular beam epitaxy of siGe virtual substrates ii strain relaxation and surface morphology
Semiconductor Science and Technology, 2000Co-Authors: J M Hartmann, B Gallas, Jiaqi Zhang, J J HarrisAbstract:We have studied the strain state, film and surface morphology of SiGe virtual substrates grown by gas-source molecular beam epitaxy (use of disilane and Germane). The macroscopic strain relaxation and the Ge composition of these virtual substrates have been estimated in high resolution x-ray diffraction, using either omega-2 theta scans or reciprocal space maps around the (004) and (224) orders. Typically, linearly graded Si0.67 Ge0.33 virtual substrates 2.5 µm thick are 97% relaxed. From transmission electron microscopy, we confirm that the misfit dislocations Generated to relax the lattice mismatch between Si and SiGe are mostly confined inside the graded layer. The surface roughness of the relaxed SiGe virtual substrates increases significantly as the Ge Concentration and/or the growth temperature exceeds 20%/600 °C. At 550 °C, we find for the technologically important Ge Concentration of 30% a surface root mean square roughness of 12 nm, with an undulation wavelength for the cross-hatch of the order of one micron.
Wenwu Wang - One of the best experts on this subject based on the ideXlab platform.
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selective wet etching in fabricating siGe nanowires with tmah solution for gate all around mosfets
Journal of Materials Science: Materials in Electronics, 2020Co-Authors: Xiaohong Cheng, Haoyan Liu, Ying Zan, Qingzhu Zhang, Jun Luo, Wenwu WangAbstract:In this work, a selective wet etching process of Si to Si0.7Ge0.3 with TMAH solution to fabricate SiGe nanowires is systematically investigated. Initially, the 2.3% TMAH solution at 20 °C is applied for the as grown Si0.7Ge0.3/Si multilayers stack and a “rectangular” profile is achieved at the Si0.7Ge0.3 extremity due to its high selectivity. However, the reduction of Ge Concentration due to the Ge interdiffusion caused by the high temperature anneal treatment will attain a reduced selectivity of Si to Si0.7Ge0.3 and a “rounding” Si0.7Ge0.3 extremity profile. Moreover, the profile of the upper Si0.7Ge0.3 extremity is clearly worse than the bottom one. This is because the Ge Concentration of upper Si0.7Ge0.3 is 1.5% lower and the Ge interdiffusion of the upper Si0.7Ge0.3 is slightly worse. After increasing the TMAH Concentration to 25%, both the upper and bottom Si0.7Ge0.3 extremity can achieve a “rectangular” extremity profile with an almost the same Si0.7Ge0.3 loss ~ 1.5 nm per side. Compared with 2.3% TMAH Concentration, the Ge Concentration of the etching off SiGe film can be reduced from lower than 29% to lower than 24% using the 25% TMAH solution at 20 °C. Therefore, the 25% TMAH solution at 20 °C is chosen as the optimal selective etching condition for the thermal treated Si0.7Ge0.3/Si multilayers stack samples. Finally, a vertical stacked double SiGe nanowire structure is successfully prepared by utilizing this optimal process condition. This indicates that it is a practicable technique for the selective wet etching of Si in fabricating SiGe nanowires.
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high crystal quality strained si0 5Ge0 5 layer with a thickness of up to 50 nm grown on the three layer siGe strain relaxed buffer
Materials Science in Semiconductor Processing, 2019Co-Authors: Zhiqian Zhao, Guilei Wang, Qingzhu Zhang, Jun Luo, Xiaolei Wang, Hong Yang, Huaxiang Yin, Wenwu WangAbstract:Abstract In this work, a novel stacking structure of three-layer SiGe strain relaxed buffer/strained Si0.5Ge0.5 layer for shallow trench isolation last scheme is successfully developed. Firstly, a three-layer SiGe epitaxy with Ge Concentration increased from bottom to top by roughly 10% combining with each layer post growth in-situ annealing is employed to effectively constrain the threading dislocation defect in the bottom and middle strain relaxed buffer layer and the top layer of strain relaxed buffer with thickness of ∼1 μm has no obviously defect impact. Before Si0.5Ge0.5 layer epitaxy on the top of this strain relaxed buffer layer, a chemical-mechanical planarization step is employed to improve surface roughness of strain relaxed buffer layer from 6.09 nm to 0.23 nm and final Si0.5Ge0.5 layer surface roughness from 6.73 nm to 0.76 nm. Finally, on the post CMP three-layer SiGe strain relaxed buffer, a smooth and high crystal quality strained Si0.5Ge0.5 layer with a thickness of 50 nm, which is larGer than its critical thickness of ∼20 nm, is successfully prepared by utilizing our new developed technique.
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a novel three layer graded siGe strain relaxed buffer for the high crystal quality and strained si 0 5 Ge 0 5 layer epitaxial grown
Journal of Materials Science: Materials in Electronics, 2019Co-Authors: Zhiqian Zhao, Guilei Wang, Qingzhu Zhang, Jun Luo, Xiaolei Wang, Hong Yang, Huaxiang Yin, Wenwu WangAbstract:In this work, a novel three-layer SiGe strain relaxed buffer/strained Si0.5Ge0.5 layer stacking structure is systematically investigated. The novel three-layer graded SiGe strain relaxed buffer, whose Ge Concentration increased from bottom to top by roughly 10% with an in situ annealing after each layer grown, can effectively constrain the threading dislocation in the strain relaxed buffer layer. Moreover, a chemical mechanical planarization process can be applied to the strain relaxed buffer to further improve its surface roughness. A high crystal quality and atomically smooth surface Si0.5Ge0.5 layer can be successfully realized on the novel chemical mechanical planarization-treated three-layer SiGe strain relaxed buffer. This strategy can attain at least 50 nm and 0.6% compressive strained Si0.5Ge0.5 layer and its quantification of the strain level is confirmed by utilizing the scanning moire frinGe imaging technique. It can be seen that this novel structure can provide a better mobility and larGer width for the FinFET or nanowire SiGe channel device.
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high crystalline quality of si 0 5 Ge 0 5 layer grown on a novel three layer strain relaxed buffer
International Conference on Electron Devices and Solid-State Circuits, 2019Co-Authors: Zhiqian Zhao, Guilei Wang, Wenwu WangAbstract:A novel three-layer graded SiGe strain relaxed buffer, whose Ge Concentration increased from bottom to top by roughly 10% with an in-situ annealing after each layer grown, is developed to effectively constrain the threading dislocation and attain a high crystalline quality of Si 0.5 Ge 0.5 layer. Moreover, a chemical mechanical planarization step can be applied to the strain relaxed buffer to further improve the surface roughness and crystalline quality of Si 0.5 Ge 0.5 layer. So, a high crystal quality and atomically smooth surface Si 0.5 Ge 0.5 layer can be successfully realized. Meanwhile, this novel three-layer graded SiGe strain relaxed buffer also can increase the critical thickness of Si 0.5 Ge 0.5 from less than 20nm to at least 50 nm and attain 0.6% compressive strain for Si 0.5 Ge 0.5 layer by utilizing the scanning moire frinGe imaging technique.
B. Svensson - One of the best experts on this subject based on the ideXlab platform.
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Lattice diffusion and surface segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge Concentration and biaxial stress.
Journal of Applied Physics, 2004Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B. SvenssonAbstract:Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge Concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segregation decreases with increasing Ge Concentration, i.e. with increased compressive stress, ii) for unstressed layers, B segregation increases with Ge Concentration, iii) at constant Ge Concentration, B segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge Concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium segregation driving force induced by Ge additions and an increase of near-surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing Ge Concentration, ii) at constant Ge Concentration, the diffusion coefficient of B decreases with compressive biaxial stress and increases with tensile biaxial stress, iii) the volume of activation of B diffusion ( ) is positive for biaxial stress while it is negative in the case of hydrostatic pressure. This confirms that under a biaxial stress the activation volume is reduced to the relaxation volume.
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diffusion of phosphorus in relaxed si1 xGex films and strained si si1 xGex heterostructures
Journal of Applied Physics, 2003Co-Authors: J. S. Christensen, Henry H Radamson, Yu A Kuznetsov, B. SvenssonAbstract:Phosphorus diffusion has been studied in relaxed Si1−xGex samples (x=0.11 and 0.19) and strained Si/Si1−xGex/Si heterostructures (x=0.08, 0.13, and 0.18). The diffusivity of P is found to increase with increasing Ge content, while the influence of compressive strain results in a decrease in diffusivity as compared to that in relaxed material. The effect of strain is found to be equivalent to an apparent activation energy of −13 eV per unit strain, where the negative sign indicates that the P diffusion is mediated by interstitials in Si1−xGex (x<0.20). This conclusion is also supported by an experiment utilizing injection of Si self-interstitials, which results in an enhanced P diffusion in strained Si1−xGex. Further, P is found to segregate into Si across Si/Si1−xGex interfaces and the segregation coefficient increases with increasing Ge Concentration.
S H Olsen - One of the best experts on this subject based on the ideXlab platform.
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influence of the Ge Concentration in the virtual substrate on the low frequency noise in strained si surface n channel metal oxide semiconductor field effect transistors
Journal of Applied Physics, 2008Co-Authors: K Fobelets, S L Rumyantsev, M S Shur, S H OlsenAbstract:We report on low frequency noise and field-effect mobility in strained-Si surface n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) grown on relaxed virtual substrates with a Ge Concentration varying between 0% and 30%. An increased Ge Concentration results in higher intrinsic field-effect mobility, increasing from 380cm2V−1s−1 for the unstrained channel to 865cm2V−1s−1 for the strained-Si MOSFET on 30% relaxed SiGe virtual substrate. However, the higher mobility is traded off for increased substrate leakaGe currents and increased 1∕f (flicker) noise. It is sugGested that flicker noise is due to traps in the oxide layer. The density of traps increases from 2×1017eV−1cm−3 for 0% Ge to 2.3×1018eV−1cm−3 for the 30% Ge virtual substrate.
J. S. Christensen - One of the best experts on this subject based on the ideXlab platform.
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lattice diffusion and surface segregation of b during growth of siGe heterostructures by molecular beam epitaxy effect of Ge Concentration and biaxial stress
Journal of Applied Physics, 2004Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B G SvenssonAbstract:Si1−xGex∕Si1−yGey∕Si(100) heterostructures grown by molecular beam epitaxy were used in order to study B surface segregation during growth and B lattice diffusion. Ge Concentration and stress effects were separated. Analysis of B segregation during growth shows that (i) for layers in epitaxy on (100)Si, B segregation decreases with increasing Ge Concentration, i.e., with increased compressive stress; (ii) for unstressed layers, B segregation increases with Ge Concentration; (iii) at constant Ge Concentration, B segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge Concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium segregation driving force induced by Ge additions and an increase of near-surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that (i) in unstressed layers, B lattice diffusion coefficient decreases with increasing...
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Lattice diffusion and surface segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge Concentration and biaxial stress.
Journal of Applied Physics, 2004Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B. SvenssonAbstract:Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge Concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segregation decreases with increasing Ge Concentration, i.e. with increased compressive stress, ii) for unstressed layers, B segregation increases with Ge Concentration, iii) at constant Ge Concentration, B segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge Concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium segregation driving force induced by Ge additions and an increase of near-surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing Ge Concentration, ii) at constant Ge Concentration, the diffusion coefficient of B decreases with compressive biaxial stress and increases with tensile biaxial stress, iii) the volume of activation of B diffusion ( ) is positive for biaxial stress while it is negative in the case of hydrostatic pressure. This confirms that under a biaxial stress the activation volume is reduced to the relaxation volume.
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diffusion of phosphorus in relaxed si1 xGex films and strained si si1 xGex heterostructures
Journal of Applied Physics, 2003Co-Authors: J. S. Christensen, Henry H Radamson, Yu A Kuznetsov, B. SvenssonAbstract:Phosphorus diffusion has been studied in relaxed Si1−xGex samples (x=0.11 and 0.19) and strained Si/Si1−xGex/Si heterostructures (x=0.08, 0.13, and 0.18). The diffusivity of P is found to increase with increasing Ge content, while the influence of compressive strain results in a decrease in diffusivity as compared to that in relaxed material. The effect of strain is found to be equivalent to an apparent activation energy of −13 eV per unit strain, where the negative sign indicates that the P diffusion is mediated by interstitials in Si1−xGex (x<0.20). This conclusion is also supported by an experiment utilizing injection of Si self-interstitials, which results in an enhanced P diffusion in strained Si1−xGex. Further, P is found to segregate into Si across Si/Si1−xGex interfaces and the segregation coefficient increases with increasing Ge Concentration.
