  The persistent interest of the epitaxy of group IV alloy GeSn is mainly
driven by the demand of efficient light source that could be monolithically
integrated on Si for mid-infrared Si photonics. For chemical vapor deposition
of GeSn, the exploration of parameter window is difficult from the beginning
due to its non-equilibrium growth condition. In this work, we demonstrated the
effective pathway to achieve the high quality GeSn with high Sn incorporation.
The GeSn films were grown on Ge-buffered Si via ultra-high vacuum chemical
vapor deposition using GeH4 and SnCl4 as precursor gasses. The influence of
both SnCl4 flow fraction and growth temperature on the Sn incorporation and
material quality were investigated. The key to achieve effective Sn
incorporation and high material quality is to explore the proper parameter
match between SnCl4 supply and growth temperature, which is also called
optimized growth regime. The Sn precipitation is significantly suppressed in
optimized growth regime, leading to more Sn incorporation into Ge and enhanced
material quality. The prototype GeSn photoconductors were fabricated with
typical samples, showing the promising devices applications towards
mid-infrared optoelectronics.
