Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 2: Symposium ZnO - Rediscovered

HL 2.2: Vortrag

Freitag, 4. März 2005, 11:15–11:45, TU P270

Electrical properties of ZnO thin films and optical properties of ZnO-based nanostructures — •M. Grundmann — Universität Leipzig, Institut für Experimentelle Physik II

We compare the electrical properties of ZnO bulk crystals and ZnO thin films grown with pulsed laser deposition with regard to carrier concentration and mobility. Both by making highly pure layers and by compensation with acceptors very low carrier concentration can be achieved (n<10¹⁴ cm⁻³). We present Schottky diodes, e.g. Pd/ZnO, of high quality (j=4 · 10⁻⁵ A/cm² at a bias of -5V, n=1.4). The quality of the contacts is limited by the lateral homogeneity of the barrier height. Using the Schottky contacts the depletion layer can be investigated (CV, DLTS, admittance). We discuss the energetic position of various shallow and deep levels in bulk and thin films detected this way. ZnO allows the fabrication a various nanostructures such as belts, sheets and pillars. The latter mostly exhibit a hexagonal cross section. Using whispering gallery modes (WGM) in the visible and UV spectral region with mode numbers down to N=1, the size and cross-sectional shape of the pillars and needles (tapered pillars) can be detected spatially resolved. The polarization-dependent WGM spectra compare rather well to numerical simulations. This work was supported by Deutsche Forschungsgemeinschaft in the framework of SPP 1136 and FOR 522 and is in collaboration with H. v. Wenckstern, R. Pickenhain, A. Rahm, Th. Nobis and M. Lorenz.