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DDC: 530 × Subject: optical properties ×

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    Optical properties of In2O3 from experiment and first-principles theory: influence of lattice screening
    ([Bad Honnef] : Dt. Physikalische Ges., 2018) Schleife, André; Neumann, Maciej D.; Esser, Norbert; Galazka, Zbigniew; Gottwald, Alexander; Nixdorf, Jakob; Goldhahn, Rüdiger; Feneberg, Martin
    The framework of many-body perturbation theory led to deep insight into electronic structure and optical properties of diverse systems and, in particular, many semiconductors. It relies on an accurate approximation of the screened Coulomb electron–electron interaction W, that in current implementations is usually achieved by describing electronic interband transitions. However, our results for several oxide semiconductors indicate that for polar materials it is necessary to also account for lattice contributions to dielectric screening. To clarify this question in this work, we combine highly accurate experimentation and cutting-edge theoretical spectroscopy to elucidate the interplay of quasiparticle and excitonic effects for cubic bixbyite In2O3 across an unprecedentedly large photon energy range. We then show that the agreement between experiment and theory is excellent and, thus, validate that the physics of quasiparticle and excitonic effects is described accurately by these first-principles techniques, except for the immediate vicinity of the absorption onset. Finally, our combination of experimental and computational data clearly establishes the need for including a lattice contribution to dielectric screening in the screened electron–electron interaction, in order to improve the description of excitonic effects near the absorption edge.
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    Structural and optical properties of (112̅2) InGaN quantum wells compared to (0001) and (112̅0)
    (Milton Park : Taylor & Francis, 2016) Pristovsek, Markus; Han, Yisong; Zhu, Tongtong; Oehler, Fabrice; Tang, Fengzai; Oliver, Rachel A.; Humphreys, Colin J.; Tytko, Darius; Choi, Pyuck-Pa; Raabe, Dierk; Brunner, Frank; Weyers, Markus
    We benchmarked growth, microstructure and photo luminescence (PL) of (112-2) InGaN quantum wells (QWs) against (0001) and (112-0). In incorporation, growth rate and the critical thickness of (112-2) QWs are slightly lower than (0001) QWs, while the In incorporation on (112-0) is reduced by a factor of three. A small step-bunching causes slight fluctuations of the emission wavelength. Transmission electron microscopy as well as atom probe tomography (APT) found very flat interfaces with little In segregation even for 20% In content. APT frequency distribution analysis revealed some deviation from a random InGaN alloy, but not as severe as for (112-0). The slight deviation of (112-2) QWs from an ideal random alloy did not broaden the 300 K PL, the line widths were similar for (112-2) and (0001) while (112-0) QWs were broader. Despite the high structural quality and narrow PL, the integrated PL signal at 300 K was about 4 lower on (112-2) and more than 10 lower on (112-0).