Energy exchange between electrons and phonons in quantum dot connected between pyramidal and abrupt transport nanojunctions

Abstract

Electron–phonon scattering induced intensive heat generation is one of the major bottlenecks for high performance nanoelectronic circuits in miniaturizing their line widths beyond submicron scales. The existence of quantum confinement effects in nanoscaled conduction channels results in which the behaviors of electrons and phonons will become drastically different from those in bulk materials. This is especially true in the junction regions where the nanochannel is linked with the electronic and thermal reservoirs. The present study investigated the structural effect of pyramidal and abrupt junctions in heat exchange between electron and phonon subsystems in the transport through a quantum dot (QD). The numerical results indicated that by confining the electronic and phononic wave functions in the pyramidal junctions, a higher saturation heat exchange would be reached at a lower bias, compared to that of the abrupt junction. The pyramidal junction also becomes more subjected to size effects, where the saturation heat exchange decreases as the size of the junction increases. Such an effect is less significant in the abrupt junctions. Surface reconstruction induced bond stiffening in the pyramidal junctions plays a dominant role in modulating the junction heat exchange by blockading the phonon transportation between the reservoirs through the QD, which effectively reducing the amount of heat being generated. The results may provide new insights on the fundamental science and relationship between contact atomic structures and thermal dissipations in nanoelectronics.