Calculated band structure of cubic GeTe (top) and rhombohedral ferroelectric GeTe showing the non-equivalent Γ-L directions (bottom). The points “L1” and “L2” are the fcc L points along the rhombohedral c-axis and non-c-axis directions, respectively. Note the differences between these two directions, e.g., in the dispersion of the lowest conduction band from Γ. The direct band gaps at “L1” and “L2” are 0.61 eV and 0.53 eV, respectively, while the indirect gap from the valence band at “L1” to the conduction band at “L2” is 0.45 eV. The lowest indirect gap is from a valence band away from a symmetry point approximately along a line joining an “L1” to an “L2” point to the “L2” point conduction band and is 0.38 eV.
Calculated optical reflection for cubic and rhombohedral ferroelectric GeTe. For the rhombohedral case, “zz” denotes polarization along the ferroelectric polar axis, while “xx” denotes in polarization perpendicular to it.
Calculated p-character projections of the electronic density of states of NaCl cubic (c) and rhombohedral (r) GeTe onto the Ge and Te LAPW spheres. The energy zero is set to the valence band maximum.
Article metrics loading...
Full text loading...