Room temperature GeSn nanowire mid-infrared photodetectors

Germanium-Tin (GeSn) alloys have recently been the subject of extensive investigations as new material systems to engineer a direct bandgap in group IV semiconductors, which will pave the way to developing silicon-compatible photonic, electronic and optoelectronic devices. The same paradigm can be extended to grow nanowires (NWs) and NW heterostructures, thus providing additional degrees of freedom to tailor the basic properties of this emerging class of semiconductors. Careful control of the growth kinetics to incorporate Sn atoms into Ge at concentrations about one order of magnitude higher than the equilibrium solubility is at the core of this technology. In this presentation, we will discuss the structural and opto-electronic properties of Ge/GeSn core/shell nanowires (NW) that are grown with a tunable, uniform Sn content exceeding 20 at.%. Single NW photodetectors operating at short-wave infrared (SWIR) and mid-infrared (MIR) wavelengths will be shown at room temperature and their properties will be investigated at cryogenic temperatures. By simultaneously increasing Sn content and minimizing strain in the GeSn shell, the absorption edge in the photocurrent measurements can be precisely tuned from ~2 μm (8 at.%) to longer MIR wavelengths.