Sn-incorporation effect on thermoelectric properties of Sb-doped Ge-rich Ge_{1- x- y} Si_x Sn_y epitaxial layers grown on GaAs(001)

We investigate Sn incorporation effects on the thermoelectrical characteristics of n-type Ge-rich Ge1-x-y Si x Sn y layers (x ≈ 0.05-0.1, y ≈ 0.03) pseudomorphically grown on semi-insulating GaAs(001) substrates by molecular beam epitaxy. Despite the low Sn content of 3%, the Sn atoms play a role in suppressing the thermal conductivity from 13.5 to 9.0 Wm-1 K-1 without degradation of the electrical conductivity and the Seebeck coefficient. Furthermore, a relatively high power factor (maximum: 14 μW cm-1 K-2 at room temperature) was also achieved for the Ge1-x-y Si x Sn y layers, almost the same as the Si1-x Ge x ones (maximum: 12 μW cm-1 K-2 at room temperature) grown with the same conditions. This result opens up the possibility of developing Sn-incorporated group-IV thermoelectric devices.