Effect of an Atomically Matched Structure on Fermi-level Pinning at Metal/p-Ge Interfaces

Using low-temperature molecular beam epitaxy (LTMBE), we demonstrate high-quality heterointerfaces consisting of CoFe alloys and germanium (Ge) with a good atomic matching at the (111) plane. Electrical properties of the atomically matched CoFe/p-Ge(111) junctions with the area of (S) < ~10 μm² clearly show the suppression of the Fermi-level pinning (FLP) effect, similar to the features of the atomically matched Fe₃Si/p-Ge(111) junctions with S < ~10 μm² in our previous work. This means that the suppression of FLP is independent on a kind of metals. As a result, we conclude that the formation of the atomically matched metal/Ge interfaces with almost no defects is important to suppress FLP.