Direct observation of hot-electron-enhanced thermoelectric effects in silicon nanodevices

The study of thermoelectric behaviors in miniatured transistors is of fundamental importance for developing bottom-level thermal management. Recent experimental progress in nanothermetry has enabled studies of the microscopic temperature profiles of nanostructured metals, semiconductors, two-dimensional material, and molecular junctions. However, observations of thermoelectric (such as nonequilibrium Peltier and Thomson) effect in prevailing silicon (Si)-a critical step for on-chip refrigeration using Si itself-have not been addressed so far. Here, we carry out nanothermometric imaging of both electron temperature (T-e) and lattice temperature (T-L) of a Si nanoconstriction device and find obvious thermoelectric effect in the vicinity of the electron hotspots: When the electrical current passes through the nanoconstriction channel generating electron hotspots (with T-e similar to 1500 K being much higher than T-L similar to 320 K), prominent thermoelectric effect is directly visualized attributable to the extremely large electron temperature gradient (similar to 1 K/nm). The quantitative measurement shows a distinctive third-power dependence of the observed thermoelectric on the electrical current, which is consistent with the theoretically predicted nonequilibrium thermoelectric effects. Our work suggests that the nonequilibrium hot carriers may be potentially utilized for enhancing the thermoelectric performance and therefore sheds new light on the nanoscale thermal management of post-Moore nanoelectronics.

Automated summary

The study of thermoelectric behaviors in miniatured transistors is crucial for bottom-level thermal management. Recent progress in nanothermetry enables the observation of temperature profiles in nanostructured materials and molecular junctions. This study addresses the thermoelectric effect in silicon and discovers the potential for on-chip refrigeration using silicon itself.