Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 7: II-VI semiconductors

HL 7.1: Talk

Monday, February 25, 2008, 11:30–11:45, EW 201

Gate induced transition from n to p conduction in HgTe quantum wells — •Christoph Brüne, Markus König, Steffen Wiedmann, Andreas Roth, Hartmut Buhmann, and Laurens W. Molenkamp — Physikalisches Institut, Lehrstuhl für Experimentelle Physik 3, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

HgTe/HgCdTe quantum well (QW) structures became very interesting for electronical applications due the good electrical properties and the unique band structure (which e.g. enabled the observation of the quantum spin hall effect [1]). In low density n-type QWs and as a consequence of the narrow bandgap it becomes possible to deplete the conduction band completely and introduce p-type conduction. The depletion can be realised by using a gate electrode to lower the fermi level in the QW. The n-to-p transition is observed in magneto transport measurements on hallbar structures. Clear SdH oscillations and hall plateus are observed in the p-type regime even though the contact regions are n-type, which leads to an additional p-n junction resistance. This Esaki-type tunnel resistance is deduced from the measurements. It turned out that the resistance and mobility changes are mainly due to a change of the effective band mass of the carriers.
[1] M. König et al. Science 318, 766 (2007).