Source–Drain Engineering Using Atomically Controlled Heterojunctions for Next-Generation SiGe Transistor Applications

Abstract

Using low-temperature molecular-beam epitaxy techniques on the (111) plane of Si or Ge, we can realize an atomically controlled Fe3Si/Si or Fe3Si/Ge heterojunction and simultaneously obtain DO3-ordered crystal structures of Fe3Si films. First, high-quality Fe3Si/Si(111) Schottky tunnel contacts enable us to inject and detect spin-polarized electrons in Si conduction channels at ∼180 K, where Fe3Si is a ferromagnetic spin injector and detector. This may lead to the accelerated development of next-generation Si-based spin metal–oxide–semiconductor field-effect transistors (MOSFETs). Next, for the atomically controlled Fe3Si/Ge(111) Schottky contacts, we find the unexpected suppression of the Fermi level pinning (FLP) effect. This indicates that there is an influence of extrinsic contributions such as dangling bonds and disorder on the strong FLP effect at metal/Ge interfaces. We expect that the Fe3Si/Ge(111) contacts can be used to control the Schottky barrier height of future ultra scaled Ge-channel MOSFETs. These two novel and interesting results are expected to form the basis of a key technology toward developing next-generation SiGe transistors.