Novel high quality GeSn alloys for mid-infrared photodetectors

Intense research interest in GeSn alloys in recent years has been fuelled by their potential for efficient light absorption in the near-to-mid infrared (IR), the possibility of mid-IR lasers, and their ready compatibility, including integration, with Si fabrication. However, the Sn solubility in Ge is only 0.5 at% and hence non-equilibrium methods must be used to produce high quality alloys with high Sn content. Conventionally, CVD has been the preferred preparation method but several challenges in producing good quality material have made efficient room temperature IR photodetectors (and lasers) out to 4 m elusive. Recently, we developed a new preparation method involving Sn ion implantation into Ge followed by pulsed laser melting (PLM) to produce both thin (strained) and thick (unstrained) alloy layers with Sn concentrations beyond 15 at%.