Composition Dependent Electrical Transport in Si_1-x Ge_x Nanosheets with Monolithic Single-Elementary Al Contacts

Si_1-x Ge_x is a key material in modern complementary metal-oxide-semiconductor and bipolar devices. However, despite considerable efforts in metal-silicide and -germanide compound material systems, reliability concerns have so far hindered the implementation of metal-Si_1-x Ge_x junctions that are vital for diverse emerging "More than Moore" and quantum computing paradigms. In this respect, the systematic structural and electronic properties of Al-Si_1-x Ge_x heterostructures, obtained from a thermally induced exchange between ultra-thin Si_1-x Ge_x nanosheets and Al layers are reported. Remarkably, no intermetallic phases are found after the exchange process. Instead, abrupt, flat, and void-free junctions of high structural quality can be obtained. Interestingly, ultra-thin interfacial Si layers are formed between the metal and Si_1-x Ge_x segments, explaining the morphologic stability. Integrated into omega-gated Schottky barrier transistors with the channel length being defined by the selective transformation of Si_1-x Ge_x into single-elementary Al leads, a detailed analysis of the transport is conducted. In this respect, a report on a highly versatile platform with Si_1-x Ge_x composition-dependent properties ranging from highly transparent contacts to distinct Schottky barriers is provided. Most notably, the presented abrupt, robust, and reliable metal-Si_1-x Ge_x junctions can open up new device implementations for different types of emerging nanoelectronic, optoelectronic, and quantum devices.