Browsing by Author "Klesse, W.M."

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    The electronic structure of ϵ-Ga2O3
    (Melville, NY : AIP Publ., 2019) Mulazzi, M.; Reichmann, F.; Becker, A.; Klesse, W.M.; Alippi, P.; Fiorentini, V.; Parisini, A.; Bosi, M.; Fornari, R.
    The electronic structure of ε-Ga2O3 thin films has been investigated by ab initio calculations and photoemission spectroscopy with UV, soft, and hard X-rays to probe the surface and bulk properties. The latter measurements reveal a peculiar satellite structure in the Ga 2p core level spectrum, absent at the surface, and a core-level broadening that can be attributed to photoelectron recoil. The photoemission experiments indicate that the energy separation between the valence band and the Fermi level is about 4.4 eV, a valence band maximum at the Γ point and an effective mass of the highest lying bands of – 4.2 free electron masses. The value of the bandgap compares well with that obtained by optical experiments and with that obtained by calculations performed using a hybrid density-functional, which also reproduce well the dispersion and density of states.
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    Lateral Selective SiGe Growth for Local Dislocation-Free SiGe-on-Insulator Virtual Substrate Fabrication
    (Pennington, NJ : ECS, 2023) Anand, K.; Schubert, M.A.; Corley-Wiciak, A.A.; Spirito, D.; Corley-Wiciak, C.; Klesse, W.M.; Mai, A.; Tillack, B.; Yamamoto, Y.
    Dislocation free local SiGe-on-insulator (SGOI) virtual substrate is fabricated using lateral selective SiGe growth by reduced pressure chemical vapor deposition. The lateral selective SiGe growth is performed around a ∼1.25 μm square Si (001) pillar in a cavity formed by HCl vapor phase etching of Si at 850 °C from side of SiO2/Si mesa structure on buried oxide. Smooth root mean square roughness of SiGe surface of 0.14 nm, which is determined by interface roughness between the sacrificially etched Si and the SiO2 cap, is obtained. Uniform Ge content of ∼40% in the laterally grown SiGe is observed. In the Si pillar, tensile strain of ∼0.65% is found which could be due to thermal expansion difference between SiO2 and Si. In the SiGe, tensile strain of ∼1.4% along 〈010〉 direction, which is higher compared to that along 〈110〉 direction, is observed. The tensile strain is induced from both [110] and [−110] directions. Threading dislocations in the SiGe are located only ∼400 nm from Si pillar and stacking faults are running towards 〈110〉 directions, resulting in the formation of a wide dislocation-free area in SiGe along 〈010〉 due to horizontal aspect ratio trapping.
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    Temperature dependence of strain–phonon coefficient in epitaxial Ge/Si(001): A comprehensive analysis
    (Chichester [u.a.] : Wiley, 2020) Manganelli, C.L.; Virgilio, M.; Skibitzki, O.; Salvalaglio, M.; Spirito, D.; Zaumseil, P.; Yamamoto, Y.; Montanari, M.; Klesse, W.M.; Capellini, G.
    We investigate the temperature dependence of the Ge Raman mode strain–phonon coefficient in Ge/Si heteroepitaxial layers. By analyzing the temperature-dependent evolution of both the Raman Ge-Ge line and of the Ge lattice strain, we obtain a linear dependence of the strain–phonon coefficient as a function of temperature. Our findings provide an efficient method for capturing the temperature-dependent strain relaxation mechanism in heteroepitaxial systems. Furthermore, we show that the rather large variability reported in the literature for the strain–phonon coefficient values might be due to the local heating of the sample due to the excitation laser used in µ-Raman experiments. © 2020 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd