Electrical and magnetic characterization of implanted GaN/AlGaN based heterostructures for spintronics applications.

This work addresses electrical and magnetic properties of GaN based heterostuctures. The potential of GaN based devices for spintronics application is discussed. The first chapter of this work gives a short review of the state-of-the-art understanding of the magnetic properties of Gd doped GaN and spin-orbit coupling in GaN/AlGaN high electron mobility structures. Chapter two addresses magnetic properties of solid states in general, while the third chapter focuses on electrotransport in mesoscopic systems. These two chapters aimto give a basis, which is necessary to understand the experimental results discussed in chapters five and six. The implemented experimental techniques are described in chapter four. Chapter five summarizes results of magnetic properties studies of Gd doped GaN performed in the framework of current thesis. It is shown that not only Gd ions themselves, but also crystal defects and oxygen impurities play a crucial role in the magnetic properties of GaN. It is also demonstrated, how oxygen implantation may increase the effective magnetic moment of the paramagnetic centers in Gd doped GaN. The sixth chapter of the work addresses the role of the spin-orbit coupling in the GaN/AlGaN high electron mobility transistor (HEMT) structures. The anomalous Halleffect in the two dimensional electron gas is demonstrated for the first time in paramagnetic Gd implanted GaN/AlGaN HEMT structures. The weak antilocalization is measured and used to calculate spin-orbit coupling in non-implanted and Ga and Gd implanted GaN/AlGaN HEMT structures.

Stepan Shvarkov received his diploma in Physics on the physics department of Belarusian Stat University in 2009. After that he has worked on his PhD thesis at the chair for applied solid-state physics at the Ruhr-University Bochum in Germany from 2009 to 2013. During this time Stepan Shvarkov developed his interest in the field of electrotransportand magnetic properties of ion implanted GaN-based semiconductors. He defended successfully his thesis with “excellence” in 2013. At the moment of this book publication Stepan Shvarkov is a post-doc in the working group Optoelectronic materials and devices in the physics department of the University of Paderborn in Germany.