Dresden 2014 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 37: Preparation and characterization
HL 37.1: Vortrag
Dienstag, 1. April 2014, 09:30–09:45, POT 151
Enhanced ferromagnetic coupling in GaMnN/GaN:Mg superlattices — •Laura Tropf1, Gerd Kunert1, Richard Wilhelm2, Sylwia Stefanowicz3, Rafal Jakiela3, Stephan Figge1, Maciej Sawicki3, Jörg Grenzer2, Tomasz Dietl3, and Detlef Hommel1 — 1Institut für Festkörperphysik, Universität Bremen — 2Ionenstrahlzentrum, Helmholtz-Zentrum Dresden-Rossendorf — 3Institute of Physics, Polish Academy of Science
GaMnN is observed to behave as a dilute magnetic insulator for Mn concentrations of up to [Mn] =10 %. As the direct incorporation of hole carriers in GaMnN, which is crucial for ferromagnetic coupling at room temperature, shows fundamental difficulties, a different approach was investigated: Superlattices were grown by molecular beam epitaxy, in which the GaMnN layers containing localized spins are separated from the p-doped GaN:Mg layers. An overlap of the hole wave function could enable ferromagnetic p-d-coupling near the interfaces.
An extensive characterization gives detailed insight on the impact the variation of the Mg-flux has on the structural and magnetic properties. Superlattices with a maximum Mn concentration of 2.6% in the GaMnN layers and Mg-densities of 4.8·1020 cm−3 in the GaN:Mg layers were obtained. This concept leads to ferromagnetic coupling at temperatures of up to 7 K, which is 6 K higher than expected from the magnetic phase diagram for undoped layers. At a certain critical Mg-flux, an abrupt reduction of the Mn- and Mg-incorporation and a deterioration of the layering could be observed and can be explained by polarity inversion from Ga-face to N-face.