Electrical And Structural Properties Of In-Implanted Si1-Xgex Alloys

We report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si1-xGex alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si1-xGex alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations of two In atoms in a Si1-xGex supercell that demonstrated that In-In pairing was energetically favorable for x less than or similar to 0.7 and energetically unfavorable for x greater than or similar to 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si1-xGex alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si1-xGex alloys, and this combination of dopant and substrate represents an effective doping protocol. (C) 2016 AIP Publishing LLC.