Abstract

Rare earth ions doped into nitride materials are known to introduce room temperature ferromagnetism into these nonmagnetic semiconductors. The origin of this dilute-magnetic semiconductor behavior remains unclear and is still heavily debated. On the other hand, if proven to be scalable in terms of layer thickness and compatible to other nitride device requirements, this finding opens the possibility to obtain spintronic devices such as spin memories and spin transistors solely based on a semiconductor with specific advantage of screening lengths and carrier nobilities. We studied such ferromagnetic layers using site-selective Zeeman spectroscopy at low temperatures. With this technique, intricate details of the magnetic interaction of the ions can be explored such as g-factors of ground and excited states including their dependence on the defect environment. Our studies reveal interesting indication of a unique coupling between the rare earth ions and the host materials. Firstly, a characteristic asymmetry in the RE ion emission strength from Zeeman-split lines. This anomalous behavior is shown in Fig. 1, in which the emission spectra are compared for applied fields parallel and antiparallel to the polar c-axis of a Nd-doped GaN sample. While in other hexagonal polar materials such as lithium niobate and tantalate these spectra are identical, a significant difference is observed. Interestingly, this difference scales with the degree of ferromagnetism observed for samples grown on different substrates.

© 2015 IEEE