Synthesis of Ge 1-xSn x alloy thin films using ion implantation and pulsed laser melting (II-PLM)

Ge _1-xSn _x thin films are interesting for all-group-IV optoelectronics because of a crossover to a direct bandgap with dilute Sn alloying. However, Sn has vanishing room-temperature equilibrium solubility in Ge, making their synthesis very challenging. Herein, we report on our attempts to synthesize Ge _1-xSn _x films on Ge (001) using ion implantation and pulsed laser melting (II-PLM). A maximum of 2 at.% Sn was incorporated with our experimental conditions in the samples as determined by Rutherford back scattering spectroscopy. A red-shift in the Ge optical phonon branch and increased absorption below the Ge bandgap with increasing Sn concentration indicate Sn-induced lattice- and band-structure changes after II-PLM. However, ion-channeling and electron microscopy show that the films are not of sufficient epitaxial quality for use in devices. © 2011 TMS.