Characterization of Mn[sub.5]Ge[sub.3] Contacts on a Shallow Ge/SiGe Heterostructure

Mn[sub.5] Ge[sub.3] is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of Mn[sub.5] Ge[sub.3] -based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of Mn[sub.5] Ge[sub.3] -based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct Mn[sub.5] Ge[sub.3] -based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that Mn[sub.5] Ge[sub.3] -based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10 e V (extracted from a Mn[sub.5] Ge[sub.3] /n-Ge analogue) and a contact resistance in the order of 1 kΩ. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability.