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

Abstract

Compressively strained Ge _1-x Sn _x 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 ${\rm{n}}({\rm{x}},\lambda )={{\rm{n}}}_{{\rm{Ge}}}(\lambda )+( \mbox{-} 2+3.5\lambda )x+5(1 \mbox{-} \lambda ){x}^{2}$ in the near-infrared range (NIR) (800–1700 nm) for Ge _1-x Sn _x alloy films. That is similar to Si _1-x Ge _x alloy films. The Hall measurement shows that the donor levels decrease due to dislocation at room temperature. Temperature dependence of the electron mobility for Ge _1-x Sn _x films reveals that strain-induced defects lower the carrier mobility from 10 K to 310 K. The maximum carrier mobility reaches 2082 cm ^2 /V·s at T = 122 K for Ge _0.96 Sn _0.04 /Ge film. These results indicate that Sn-doping has great influences on electronic properties for Ge _1-x Sn _x alloys. Our investigations may be helpful for fabricating the high performance optoelectronic devices.

Keywords

• Ge1−xSnx alloy films
• structure
• spectroscopic ellipsometer
• hall measurement