Epitaxy of Pseudomorphic GeSn Layers with Germane (GeH_4) or Digermane (Ge_2H_6) as Ge Precursors and Tin Tetrachloride (SnCl_4) as the Sn Precursor

摘要

In CEA-LETI, GeSn/SiGeSn stacks are typically grown at 100 Torr with Ge_2H_6, Si_2H_6 and SnCl_4 and temperatures in the 301°C-363°C range. Ge_2H_6 has however a reputation of being unstable for high concentrations (10% in H_2). The short shelf time can be adressed by switching over to lower concentrations and regularly changing bottles, which is complex as Ge_2H_6 is costly and complicated to order. One solution could be to switch from digermane to germane, which was shown by several R&D institutes to yield high quality GeSn layers. The epitaxy tools used, then, were capable of Atmospheric Pressure CVD (i. e. @ 760 Torr), while we have Reduced Pressure CVD chambers that can operate only up to a few hundreds of Torr.