Electrical Transport Involving Evanescent States in III-V Semiconductors: The Role of Spin-Orbit-Coupling
Final Report Abstract
Spin-dependent tunneling which is closely connected to the characteristics of evanescent states is of growing importance in spintronics. Several theoretical studies have predicted that spin-orbit coupling may have a significant impact on transport via these channels as compared with transport involving the real part of the band structure. This project has focused on the atomic scale investigation of spinorbit-coupling effects (Dresselhaus/Rashba) on evanescent wave functions with energies in the fundamental band gap of semiconductor materials and nanostructures. Our experimental approach is mainly based on scanning tunneling microscopy (STM) and related techniques (e.g., scanning tunneling spectroscopy STS) at low temperature which offer atomic scale information of the spatial and directional dependence of electronic transport described in terms of complex band structures. STM/STS in combination with electric fields have been used to investigate the electronic properties of single defects (shallow donors and acceptors) below the GaAs(110) surface as well as III-V heterostructures. One of the goals of this project was a better understanding of the imaging process of the STM of shallow donors and acceptors. In detail, we have studied the transport across acceptors in GaAs, the ionization process of single and coupled donors below the GaAs(110) surface and resonant tunneling diode structures. In a second part, the magnetic properties of the Fe/GaAs(110) interface have been investigated by magneto-optical Kerr effect (MOKE). Ultrathin ferromagnetic Fe layers have been grown epitaxially on the GaAs(110) surface. The interface has been studied by cross-sectional STM and STS. For Fe film thicknesses of 2-3 ML MOKE measurements reveal an out-of-plane magnetization unidirectionally coupled to the in-plane magnetization component along <001>. This is directly related to the inversion asymmetry of the GaAs{110} surface in the same direction and shows a strong indication of spin-orbit coupling at this interface. This coupling can be controlled by either the thickness of the Fe film or the quality of the Fe/GaAs(110) interface.
Publications
- Controlled Charge Switching on a Single Donor with a Scanning Tunneling Microscope, Phys. Rev. Lett. 101, p. 076103 (2008), selected as Research Highlight, Nature Materials 7, 764 (2008)
K. Teichmann, M. Wenderoth, S. Loth, R. G. Ulbrich, J. K. Garleff, A. P. Wijnheijmer, and P. M. Koenraad
- Enhanced Donor Binding Energy Close to a Semiconductor Surface, Phys. Rev. Lett. 102, p. 166101 (2009)
P. Wijnheijmer, J. K. Garleff, K. Teichmann, M. Wenderoth, S. Loth, R. G. Ulbrich, P. A. Maksym, M. Roy, and P. M. Koenraad
- Bistable Charge Configuration of Donor Systems near the GaAs(110) Surfaces, Nano Letters 11, p. 3538 (2011)
K. Teichmann, M. Wenderoth, S. Loth, J. K. Garleff, A. P. Wijnheijmer, P. M. Koenraad, and R. G. Ulbrich
- Single Si dopants in GaAs studied by scanning tunneling microscopy and spectroscopy, Phys. Rev. B 84, p. 125310 (2011)
P. Wijnheijmer, J. K. Garleff, K. Teichmann, M. Wenderoth, S. Loth, and P. M. Koenraad
- “Scanning tunneling spectroscopy of space charge regions in semiconductors: From single donor to heterostructure systems”, Dissertation, Georg-August-Universität Göttingen, 2012
K. Teichmann
- Fixing the Energy Scale in Scanning Tunneling Microscopy on Semiconductor Surfaces, Phys. Rev. Lett. 111, 216802 (2013)
Gerhard Münnich, Andrea Donarini, Martin Wenderoth, and Jascha Repp
(See online at https://doi.org/10.1103/PhysRevLett.111.216802) - Harmonic Oscillator Wave Functions of a Self-Assembled InAs Quantum Dot Measured by Scanning Tunneling Microscopy, Nano Letters 13, p. 3571 (2013)
K. Teichmann, M. Wenderoth, H. Prüser, K. Pierz, H. W. Schumacher, and R. G. Ulbrich
(See online at https://doi.org/10.1021/nl401217q) - Local Density of States at Metal-Semiconductor Interfaces: An Atomic Scale Study, Phys. Rev. Lett. 114, p. 146804 (2015)
T. Iffländer, S. Rolf-Pissarczyk, L. Winking, R. G. Ulbrich, A. Al-Zubi, S. Blügel, and M. Wenderoth
(See online at https://doi.org/10.1103/PhysRevLett.114.146804) - “Electronic and Magnetic Properties of the Fe/GaAs(110) Interface”, Dissertation, Georg-August-Universität Göttingen, 2015
T. Iffländer
