Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 52: Transport properties
HL 52.8: Vortrag
Freitag, 30. März 2007, 12:45–13:00, H14
Photo-induced charge transport in metal–insulator–metal (MIM) multilayer structures — •Domocos Kovacs1, Jörg Winter1, and Detlef Diesing2 — 1Institut für Experimentalphysik II, Ruhr-Universität Bochum, 44801 Bochum — 2Institut für Physikalische Chemie, Universitat Duisburg-Essen, 45141 Essen
The dependence of the photoinduced current in aluminium– alumina–top metal tunnel structures was investigated as a function of the bias voltage at three different wavelengths (266, 355, and 532 nm) of a Nd-YAG laser. With the top metal (Ag, Au) being illuminated, a net current flowing from the top electrode to the bottom electrode at zero bias for all wavelengths is measured. The photocurrent can be modified by a bias voltage applied between the two metals. For each wavelength there is a certain bias value for which the net photo current vanishes. The dependence of the measured current-voltage curves on the top electrode material and on its thickness is reported. The experimental results are compared with the calculations of a model which includes photo-absorption, electronic excitation, and charge transport in both metal electrodes represented by free electron gases and in the oxide layer described by an asymmetric tunnel barrier allowing both electron and hole tunnelling. Based on this model the influence of the metal thickness on the bias dependence of the photo-current will be discussed in terms of the photo-excited carriers lifetime.