Regensburg 2002 – scientific programme

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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.71: Poster

Thursday, March 14, 2002, 15:30–18:00, D

Oscillations, Synchronization, and Open-Loop Control in Electrochemical Semiconductor Pore Etching — •Jens Christian Claussen, Jürgen Carstensen, Marc Christophersen, Sergiu Langa, and Helmut Föll — Allgemeine Materialwissenschaft, Technische Fakultät der Universität Kiel, Kaiserstr. 2, 24143 Kiel, Germany

Electrochemical Etching of Semiconductors can result in a rich variety of porous structures from 2 nm to 50 µm and various structures with morphologies from regular pores to branched pores similar to dendritic structures. While direct local observations during etching processes are not available in general, the underlying etching process seems to be understood by the Current Burst Model [Föll, Carstensen]. This model already has supported a large variety of experimental observations by detailed numerical simulations. In this paradigmatic approach, carriers locally are transported only through charge quantizing current bursts, corresponding to a breakthrough of the oxide layer, resulting in a lateral and temporal effect on subsequent bursts: On neighboring sites current bursts are inhibited; on the same site the burst probability is zero for a fixed oxidation time, then reaches a maximum followed by a decay due to chemical surface passivation. This behavior appears to be different for the main crystallographic directions which has direct implications on the pore morphologies. – Applying a small additional sinus wave to the etching current (i. e. an open-loop control method), the dendritic-like pores can be stabilized to non-branching pores, however with oscillating diameter. In InP even self-sustained and synchronized oscillations of the pore diameters accompanied by voltage oscillations have been obtained.