Spin injection in MnGa/ GaN heterostructures

by Christian Zube
Doctoral thesis
Date of Examination:2015-11-13
Date of issue:2016-01-12
Advisor:Prof. Dr. Angela Rizzi
Referee:Prof. Dr. Angela Rizzi
Referee:Prof. Dr. Markus Münzenberg
Persistent Address: http://dx.doi.org/10.53846/goediss-5457

 

 

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Abstract

English

Due to the perfect epitaxial match of ferromagnetic MnGa on GaN and spin transport properties of GaN (long spin life time), the hybride MnGa/GaN is a promising material for future spintronic devices to examine. The samples are grown by Molecular Beam Epitaxy (MBE) on GaN tem- plates or on a pre-grown LED structure. The growth process has been monitored in-situ with reflexion high energy electron diffraction (RHEED) to investigate the epitaxial match between ferromagnet and semiconductor. The deduced epitaxial relation has been verified by transmission electron mi- croscopy (TEM). Furthermore, structural and magnetic properties of MnGa/ GaN hybrides has been assessed by x-ray diffraction (XRD), superconducting quantuum interference device (SQUID) and vibrating sample magnetometry (VSM). For the determination of the governing transport process across the MnGa/ GaN interface, transmission line features have been structured in a clean- room environment. The characterization has been done in a continuous flow cryostat with DC and AC measurement techniques. The best conditions for efficient spin injection have been found. Two different spin detection mechanisms have been employed. An all elec- trical approach which includes the preparation of sub µm structures with electron beam lithography, and an optical setup based on the analysis of the emitted light of a LED with MnGa electrodes.
Keywords: MBE, spintronic, GaN, LED
 
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