AVS 57th International Symposium & Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP4
Band and Dielectric Discontinuities of the Si1-xGex/Si1-yCy Superlattices

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Session: Nanometer-Scale Science and Technology Poster Session
Presenter: T. Ohsugi, The University of Electro-Communications (UEC-Tokyo), Japan
Authors: T. Ohsugi, The University of Electro-Communications (UEC-Tokyo), Japan
J. Nakamura, The University of Electro-Communications (UEC-Tokyo), Japan
Correspondent: Click to Email

Si1-xGex and Si1-yCy alloys have attracted much attention from the perspective of the fabrication of novel devices, e.g., resonant tunneling diodes with strained alloys [1] and hetero bipolar transistors with double quantum wells [2]. It has been known that the lattice constants of these alloys are approximately proportional to their compositional ratios in accordance with Vegard’s law [3]. Further, it has been reported that the band-gap of Si1-xGex, other than the lattice constant, changes with its composition [4]. In this study, we draw attention to the dependence of the dielectric constant on the composition of Si1-xGex and Si1-yCy as well as the dependence of other physical quantities such as lattice constants and band-gaps. We explore the band discontinuity and the spatial modulation of dielectric constants for the Si1-xGex/Si1-yCy superlattices as novel device structures, using first-principles ground-state calculations in external electric fields [5, 6].

We have adopted the cubic supercells containing 8 atoms for the Si1-xGex and Si1-yCy bulk models. It has been shown that the lattice constants of Si1-xGex and Si1-yCy alloys increase and decrease linearly with their compositions, respectively, obeying the Vegard’s law. In contrast, the nonlinearity with the composition is found for the band gap and the dielectric constants. In our presentation we discuss the origin of the onset of the nonlinearity and report the band and dielectric discontinuities of the Si1-xGex/Si1-yCy superlattices from an atomic scale point of view.

[1] P. Han et al., J. Crystal Growth, 209, 315 (2000)

[2] D. C. Houghton et al., Phys. Rev. Lett 78 2441 (1997)

[3] W. Windl et al., Phys. Rev. B 57 2431 (1998)

[4] J. Weber et al., Phys. Rev. B 40 5683 (1989)

[5] J. Nakamura et al., J. Appl. Phys. 99, 054309 (2006); Appl. Phys. Lett. 89, 053118 (2006)

[6] S. Wakui et al., J. Vac. Sci. Technol. B 26, 1579 (2008)