Authors: F. Mirando, L. Ferre Llin, D.J. Paul
The optimum thermoelectric efficiency of the main commercial microelectronic semiconductors, such as Si, Ge and Si(1-x)Ge(x), lies at high temperatures (~1000 °C). However, in Si-like alloys, the peak of the thermoelectric figure of merit could be translated towards lower temperatures through the tuning of the material doping level. Thereby, 23 µm thick
Si0.7Ge0.3 layers, grown by chemical vapour deposition (CVD) on top of silicon on insulator wafers, were doped at 1x10^19 cm^(-3) intending to shift the thermoelectric performance peak towards 500 °C. The optimal module design has then been investigated assuming a 1 cm^2 device having thermoelectric legs length of 20 µm and operating at 500 °C under constant heat flow and in presence of air thermal conduction and convection. The microfabricated thermoelectric module (128 legs of 200 µm width) is expected to produce a power output of 2.8 mW/cm^2 together with a Seebeck voltage output per degree Kelvin of 35 mV/K.