Energy
harvesting for Internet of Things applications, comprising
sensing, life sciences, wearables, and communications, requires efficient
thermoelectric (TE) materials, ideally semiconductors compatible with
Si technology. In this work, we investigate the potential of GeSn/Ge
layers, a group IV material system, as TE material for low-grade heat
conversion. We extract the lattice thermal conductivity, by developing
an analytical model based on Raman thermometry and heat transport
model, and use it to predict thermoelectric performances. The lattice
thermal conductivity decreases from 56 W/(m·K) for Ge to 4 W/(m·K)
by increasing the Sn atomic composition to 14%. The bulk cubic Ge0.86Sn0.14 alloy features a TE figure of merit of
ZT ∼ 0.4 at 300 K and an impressive 1.04 at 600 K. These values
are extremely promising in view of the use of GeSn/Ge layers operating
in the typical on-chip temperature range.