Germanium-tin semiconductors: A versatile silicon-compatible platform

Compound semiconductor alloys have been successfully used for a precise and simultaneous control of lattice parameters and bandgap structures bringing to existence a variety of functional heterostructures and low-dimensional systems. Extending this paradigm to group IV semiconductors will be a true breakthrough that will pave the way to creating an entirely new class of silicon-compatible ultra-fast/low-power electronic, optoelectronic, and photonic devices. With this perspective, germanium-tin (Ge1-xSnx) and germanium-silicon-tin (Ge1-x-ySixSny) alloys have recently been the subject of extensive investigations as new material systems to independently engineer lattice parameter and bandgap energy and directness. The ability to incorporate Sn atoms into silicon and germanium at concentrations about one order of magnitude higher than the equilibrium solubility is at the core of these emerging potential technologies. In this presentation, we will address the epitaxial growth and stability of these metastable semiconductors. We will also discuss the optical and electronic properties as well as the nature of the atomic order in Sn-rich group IV semiconductors. We will show that lattice strain engineering is critical to facilitate the incorporation of Sn at concentrations reaching, for in stance, nearly 20at.% in GeSn while suppressing Sn surface segregation and composition gradient. The basic properties of these GeSn layers will be discussed in the light of extensive optical and microscopic investigations. Moreover, we will also demonstrate that GeSn can be effectively used as a template to grow highly tensile strained Ge quantum wells. Results of the investigations of electronic properties of these new family of low-dimensional systems will be discussed. This includes the effects on strain level and nature (compressive vs. tensile) on charge carriers confinement and mobility. Finally, new concepts involving Ge/GeSn core-shell nanowires will be presented and their potential as versatile building blocks for electronics, integrated photonics, and quantum information will be addressed. Please click Additional Files below to see the full abstract