Ex-situ n-type heavy doping of Ge1-xSnx epilayers by surface Sb deposition and pulsed laser melting

Ge1-xSnx alloys have attracted considerable attention for their promising electrical and optical properties. One of the main challenges for their successful implementation in devices concerns the fabrication of n-type heavily doped surface layers. In this work, a new methodology for ex-situ doping of Ge1-xSnx layers is investigated. It consists of the deposition of Sb atoms on the surface of Ge1-xSnx layers followed by pulsed laser melting (PLM) that ensures the diffusion of Sb into the alloy. We demonstrate that Sb is incorporated very efficiently within a relaxed Ge0.91Sn0.09 epilayer, with supersaturated 4 x 10(20) cm(-3) active concentrations, in line with literature records obtained in Ge1-xSnx with in-situ approaches. At the same time, we observe that the concentration of substitutional Sn close to the surface decreases from 9 to about 6 at. % after PLM, inducing a contraction of the lattice parameter perpendicular to the underlying Ge1-xSnx. These results demonstrate a possible route for ex-situ n-type heavy doping of Ge1-xSnx alloys, but indicate also that Sn redistribution and precipitation phenomena need to be carefully considered for a successful process development.

Automated summary

Ge1-xSnx alloys have promising electrical and optical properties, but one of the challenges in implementing them in devices is the fabrication of n-type heavily doped surface layers. This study investigates a new methodology for ex-situ doping of Ge1-xSnx layers, which involves the deposition of Sb atoms on the surface followed by pulsed laser melting to facilitate diffusion. The results demonstrate efficient incorporation of Sb and provide insights into Sn redistribution and lattice parameter contraction, highlighting the importance of considering these factors for successful process development.