Injection of spin-polarized current in a Ge- based magnetic device with coplanar contacts

Electron spin injection and spin detection in magnetic materials are key features to the
functionalization of electron spin polarization as a degree of freedom for both information processing and storage. Currently, spin-dependent tunneling in magnetic junction devices is the most common approach to achieve efficient spin injection. However, many recent studies highlighted the interesting possibility to create spin-polarized currents in structures which combine a magnetic semiconductor, e.g. magnetic alloys based on group-IV semiconductors or diluted magnetic semiconductor compounds, forming a Schottky-like rectifying junction with a
metallic ferromagnet. Although theoretical works have already addressed the performance of this structure by numerical simulations of the spin drift and spin diffusion equations, taking into account various characteristics of the ferromagnet (FM) / semiconductor (SC) interface such as barrier height and boundary roughness in 1D models, correlations with experimental results are scarce.
This work aims at achieving spin injection with Ge-based magnetic structures using a rectifying junction in a coplanar architecture. We performed 2D numerical calculations of the spin drift and diffusion process in the direct neighborhood of a junction consisting of a Mn5Ge3 half-metallic ferromagnet acting as the injecting contact and an n-type Ge film, forming 3- and 4-terminal devices (Fig. 1). Our results show that geometrical effects play a major role on the spin
injection efficiency. Moreover, the simulations emphasize the asymmetry of spin accumulation at the FM/SC interface as well as a strong effect of the depletion layer caused by the Schottky contact junction. We report values of spin polarization related potential differences higher than 5 μV for a bias of 1 mV, in agreement with previous experimental results.