"Terahertz and Far Infrared Ellipsometry Studies of Charge and Lattice Dynamics in Semiconductor and Metal Nanostructures Under Strong External Fields"

Mathias Schubert, Tino Hofmann, Craig M. Herzinger

We review our recent applications of spectroscopic ellipsometry at far infrared and terahertz frequencies to study dynamics of free charger carriers and bound lattice modes in semiconductor and metal structures with one or two nanoscale dimensions when brought into strong external magnetic and electric fields. Recent improvement of our instrumentation allowed us to study the magneto optic response of Graphite at liquid helium temperatures using synchrotron-based light sources for the ellipsometric investigations.  Resonant excitations of Landau transition between hole and electron states split by quantum regimes reveal insights into the band structure of graphite, for example. We also report on our newly developed technique; the Optical Hall effect, which determines free charge carrier properties in semiconductor devices structures. Examples include surface depletion and accumulation layer properties in GaN and InN.  External electric field-dependent experiments on chiral nanowires forming arrays of inductances and capacitances reveal properties relevant for active or passive terahertz devices.

The Optical Hall Effect, T. Hofmann, C.M. Herzinger, C. Krahmer, K. Streubel, and M. Schubert, phys. stat. sol. (a) 205, 779 (2008)

Electron Effective Mass and Phonon Modes in GaAs Incorporating Boron and Indium, T. Hofmann, M. Schubert, G. Leibiger, and V. Gottschalch, Appl. Phys. Lett. 90, 182110 (2007)

Terahertz Magnetooptic Generalized Ellipsometry Using Synchrotron and Black-Body Radiation, T. Hofmann, U. Schade, W. Eberhardt, C. M. Herzinger, P. Esquinazi, and M. Schubert, Rev. Sci. Inst. 77, 063902 (2006)