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HL: Halbleiterphysik

HL 9: Poster I

HL 9.80: Poster

Montag, 27. März 2006, 15:15–17:45, P3

The role of quantum capacitance in coupled low-dimensional electron systems — •Bastian Marquardt¹, Marco Ruß¹, Cedrik Meier¹, Axel Lorke¹, Dirk Reuter², and Andreas D. Wieck² — ¹Experimental Physics, University of Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany — ²Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44799 Bochum, Germany

We have investigated the charging behavior of a layer of self-assembled InAs quantum dots placed in close vicinity to a two-dimensional electron gas (2DEG). As the gate bias is changed, the charging states of both systems are altered simultaneously. Based on the quantum capacitance of the involved layers we develop a general model to determine the charging state of coupled low-dimensional electron systems from capacitance-voltage (CV) spectroscopy. The model is then applied to the special case of a layer of self-assembled quantum dots, coupled to a 2DEG. As a complementary method to detect the carrier densities we have employed Hall voltage measurements. We find that the measurement of the two-dimensional carrier density through lateral transport provides a direct insight into the vertical charging process of the quantum dot system. In agreement with results from CV spectroscopy Coulomb blockade and quantization energies can be extracted. Moreover, the Hall measurement offers a higher peak to valley ratio and a better estimate for the number of simultaneously charged dots than the capacitance data. This novel DC transport spectroscopy is particularly promising for structures with very slow tunneling times, such as single electron memory devices.