Experimental demonstration of spreading resistance effect in a miniaturized bileg thermoelectric generator

The effect of the spreading resistance on the bileg thermoelectric generator (TEG) performance was experimentally evaluated. In planar bileg-TEGs, the width ratio of the p- and n-type legs should be carefully selected to compensate for the impedance mismatch between them and to maximize thermoelectric power generated from a unit area. In the bileg-TEG at the μm-scale, the electrical resistance becomes larger than a simple estimate using lumped parameter circuit model, which is caused by the spreading resistance; when a current flows from a narrower leg to a wider leg. A distance of greater than about 10 μm is required to distribute the electric current over the entire region of the wider leg. At shorter leg lengths, it is better to align the widths of p- and n-legs to maximize the areal power density of TEG. Decreasing the electrical resistance of the wiring between the p- and n-legs is also effective in enhancing the performance of the miniaturized TEG. The width of the p- and n-type legs in the bileg-TEG at the μm-scale should be carefully selected.