Dilute Pb in Ge materials fabricated by ion implantation and pulsed laser melting

Abstract

Germanium lead (GePb) alloys have shown promising potential as a material platform for fabricating mid-infrared photodetectors, where the Pb content enables tuning of the bandgap. However, fabricating such devices using GePb is challenging because the equilibrium solid solubility of Pb in Ge is in the parts per million range. Here, we synthesize the metastable GePb alloy by Pb implantation into Ge, followed by pulsed laser melting. By varying the ion implantation and melting conditions, we identify a processing window that yields GePb alloy films of high crystalline quality, with a substitutional Pb amount of at least 1.6 × 1015 Pb atoms/cm2, which is equivalent to a Pb concentration of around 0.36 at. %, more than 3 orders of magnitude above the equilibrium solubility. These results establish a pathway to fabricating GePb for mid-infrared photodetection applications using non-equilibrium ion implantation, ultra-rapid melting, and solidification.