Optoelectronic properties for the compressively strained Ge1−xSnx films grown on Ge(004)

Compressively strained Ge1-xSnx films (x = 0.04, 0.08, 0.14) have been grown on Ge(004) substrates by Molecular Beam Epitaxy. The wavelength dependence of the refractive index is deduced as n ( x , λ ) = n Ge ( λ ) + ( - 2 + 3.5 λ ) x + 5 ( 1 - λ ) x 2 in the near-infrared range (NIR) (800-1700 nm) for Ge1-xSnx alloy films. That is similar to Si1-xGex alloy films. The Hall measurement shows that the donor levels decrease due to dislocation at room temperature. Temperature dependence of the electron mobility for Ge1-xSnx films reveals that strain-induced defects lower the carrier mobility from 10 K to 310 K. The maximum carrier mobility reaches 2082 cm2/V s at T = 122 K for Ge0.96Sn0.04/Ge film. These results indicate that Sn-doping has great influences on electronic properties for Ge1-xSnx alloys. Our investigations may be helpful for fabricating the high performance optoelectronic devices.