Objective
Recently, first steps towards the realization of semiconductor electronics based on the precise manipulation of an electron spin instead of an electron charge - so called spin-electronics or "spintronics" - have been made by the demonstration of an efficient injection of spin-polarized carriers from magnetic to non-magnetic semiconductors. New device concepts have already started to emerge, involving spin-based transistors, opto-electronic spin devices, spin memory, or even spin quantum computers. However, the success of spin-electronics relies on the ability to create, transfer, manipulate and store spin coherence at high temperatures, without external magnetic field and over practical time and length scale.
The proposed Project implies research covering a wide spectrum of basic technological, magneto-optical, electro-optical, and transport studies of III-V, II-VI and hybrid III-V/II-VI nanostructures lattice-matched to GaAs and InAs, aimed at the exploration and development of physical principles, designs and technological basis of novel functional elements of semiconductor spin-electronics. Molecular beam epitaxy allowing control of composition and doping in semiconductor heterostructures on a monoatomic scale has been chosen as a main technological method.
The main Project objectives concern practically all the key issues of spin-electronic devices, related to injection, transportation, switching and detection of the electron spin in both longitudinal and transverse device geometries with respect to the heterostructure growth axis. In particular, a single semiconductor heterostructure concept of electrical spin injection and optical detection will be realized, using different available material systems, such as paramagnetic ZnMgMnSSe/GaAs, CdMgMnSe/InAs and ferromagnetic p-GaMnAs/GaAs ones. An idea of employing an ESAKI tunnelling diode for the transformation of holes, spin-polarized in a p-doped ferromagnetic spin-aligner, into spin-polarized electrons, travelling in n-doped semiconductor layer with a long dephasing time, throws a real bridge to high-temperature spin-electronics.
Spin switching by external voltage will be studied on the basis of spin sensitive resonant tunneling nanostructures with magnetic quantum wells or self-organized magnetic quantum dots, using the effect of the giant Zeeman splitting of a resonance energy level. Special accent will be put on the fabrication and study of Mn- contained II-VI semiconductors exhibiting hole-mediated ferromagnetic ordering due to optical pumping of the type II ZnMnTe/CdSe QW heterostructures with enhanced carrier lifetime. Particular attention will be given to growth and optical studies of magnetic quantum dots - the key element of most proposed spintronic devices. Single-quantum-dot magneto-optical spectroscopy of excitonic magnetic polarons will be applied to understand the magnetic properties of individual quantum dots.
Call for proposal
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89081 Ulm
Germany