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Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 21: Transport properties I

HL 21.9: Talk

Tuesday, March 28, 2006, 18:30–18:45, BEY 118

Photoexcited electron and hole transport in thin film tunnel systems — •Peter Thissen1, Domokos Kovacs2, Jörg Winter2, Eckart Hasselbrink1, and Detlef Diesing11Institut für Physikalische Chemie, Universität Duisburg Essen — 2Institut für Experimentalphysik 2, Ruhr Universität Bochum

The photoeffect in semiconductor based devices is often discussed as transport of the majority carriers across the metal–semiconductor interface. The photoexcited charge carriers propagate over the Schottky barrier (Ebarrier ≈ 0.7  eV for silicon–metal interfaces). In tunnel barrier systems (metal1metal1oxide–metal2) with thin oxide layers (≈ 3 nm ) and metal films (10 - 70 nm ) other transport channels may also contribute to the measured photocurrent: 1. tunneling of electrons through the conduction band barrier. 2. tunneling of holes through the valence band barrier. 3. excitation of charge carriers both in the top and in the ground metal film of the tunnel device. By applying a bias voltage between the metals, the band structure of the tunnel device can be changed allowing a discrimination between the different transport channels. Photoinduced tunnel currents (h· ν = 1.53, 1.37, 1.27   eV < Ebarrier = 1.8  eV ) were investigated as well as photoinduced UV-electronic excitations (h· ν = 11 eV >> Ebarrier ) with different bandstructures in the the tunnel devices. The investigations show a clear contribution of hot hole induced tunnel currents to the measured photo current even in the low energy range. Transport effects of excited charge carriers in the metal films are discussed refering to experiments with variable metal film thicknesses.

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