Top-Down Silicon Nanowire-Based Thermoelectric Generator: Design and Characterization

A silicon nanowire (SiNW) array-based thermoelectric generator (TEG) was assembled and characterized. The SiNW array had pitch of 400 nm, and SiNW diameter and height of <100 nm and ~1 μm, respectively. The SiNW array was formed using a top-down approach: deep-ultraviolet (UV) lithography and dry reactive-ion etching. Specific groups of SiNWs were doped n- and p-type using ion implantation, and air gaps between the SiNWs were filled with silicon dioxide (SiO2). The bottom and top electrodes were formed using a nickel silicidation process and aluminum metallization, respectively. Temperature difference across the TEG was generated with a heater and a commercial Peltier cooler. A maximum open-circuit voltage of 2.7 mV was measured for a temperature difference of 95 K across the whole experimental setup, corresponding to power output of 4.6 nW. For further improvement, we proposed the use of polyimide as a filler material to replace SiO2. Polyimide, with a rated thermal conductivity value one order of magnitude lower than that of SiO2, resulted in a larger measured thermal resistance when used as a filler material in a SiNW array. This advantage may be instrumental in future performance improvement of SiNW TEGs.