Schottky barrier tuning via dopant segregation in NiGeSn-GeSn contacts

We present a comprehensive study on the formation and tuning of the Schottky barrier of NiGeSn metallic alloys on Ge1-xSnx semiconductors. First, the Ni metallization of GeSn is investigated for a wide range of Sn contents (x = 0–0.125). Structural analysis reveals the existence of different poly-crystalline NiGeSn and Ni3(GeSn)5 phases depending on the Sn content. Electrical measurements confirm a low NiGeSn sheet resistance of 12 Ω/□ almost independent of the Sn content. We extracted from Schottky barrier height measurements in NiGeSn/GeSn/NiGeSn metal-semiconductor-metal diodes Schottky barriers for the holes below 0.15 eV. They decrease with the Sn content, thereby confirming NiGeSn as an ideal metal alloy for p-type contacts. Dopant segregation for both p- and n-type dopants is investigated as a technique to effectively modify the Schottky barrier of NiGeSn/GeSn contacts. Secondary ion mass spectroscopy is employed to analyze dopant segregation and reveal its dependence on both the Sn content and biaxial layer strain