Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 21: Transport properties I

HL 21.8: Vortrag

Dienstag, 28. März 2006, 18:15–18:30, BEY 118

Mobility Enhancement of Shallow Modulation Doped GaAs/AlGaAs Heterostructures by Presence of Metal at the Surface — •Holger Welsch, Christian Heyn, and Wolfgang Hansen — Universität Hamburg, Institut für Angewandte Physik, Jungiusstrasse 9-11, 20355 Hamburg

We perform magneto-transport measurements on shallow modulation doped GaAs/AlGaAs heterostructures. Compared to standard structures, where the two-dimensional electron gas (2-DES) is unaffected of surface states, shallow structures need higher doping in order to prevent depletion of the 2-DES. High doping concentrations as well as small spacer layers, both applied at shallow structures, are normally accompanied by reduced mobility due to scattering of the 2-DES electrons at ionised donators in the doping layer. On account of this, the minimum distance between 2-DES and surface is limited by vanishing carrier density and reduced mobility. Here we compare shallow heterostructures with open and metal coated surfaces. We find that surface metal coating on samples with a 2-DES 23 nm beneath the surface feature an up to three times higher mobility compared to the uncoated ones.