Phonon populations and electrical power dissipation in carbon nanotube transistors

• Published in: Nature nanotechnology Vol. 4; no. 5; pp. 320 - 324
• Main Authors: Avouris, Phaedon, Steiner, Mathias, Freitag, Marcus, Perebeinos, Vasili, Tsang, James C, Small, Joshua P, Kinoshita, Megumi, Yuan, Dongning, Liu, Jie
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2009; Nature Publishing Group
• Subjects: Anharmonicity; Carbon; Carbon nanotubes; Chemistry and Materials Science; Circuits; Conductance; Current carriers; Decay; Electric power; Electron transport; Electronic circuits; Electronic devices; Electronic equipment; Energy; Energy charge; Energy Transfer; Equipment Design; Equipment Failure Analysis; Graphene; Lasers; letter; Materials Science; Materials selection; Materials Testing; Nanotechnology; Nanotechnology - instrumentation; Nanotechnology and Microengineering; Nanotubes; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Particle Size; Phonons; Populations; Resistance; Scattering; Semiconductor devices; Substrates; Temperature; Transistors; Transistors, Electronic; United States > US
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/nnano.2009.22

Carbon nanotubes and graphene are candidate materials for nanoscale electronic devices 1 , 2 . Both materials show weak acoustic phonon scattering and long mean free paths for low-energy charge carriers. However, high-energy carriers couple strongly to optical phonons 1 , 3 , which leads to current saturation 4 , 5 , 6 and the generation of hot phonons 7 . A non-equilibrium phonon distribution has been invoked to explain the negative differential conductance observed in suspended metallic nanotubes 8 , while Raman studies have shown the electrical generation of hot G-phonons in metallic nanotubes 9 , 10 . Here, we present a complete picture of the phonon distribution in a functioning nanotube transistor including the G and the radial breathing modes, the Raman-inactive zone boundary K mode and the intermediate-frequency mode populated by anharmonic decay. The effective temperatures of the high- and intermediate-frequency phonons are considerably higher than those of acoustic phonons, indicating a phonon-decay bottleneck. Most importantly, inclusion of scattering by substrate polar phonons is needed to fully account for the observed electronic transport behaviour. Carbon nanotubes and graphene are potential components for nanoscale electronic devices, but power dissipation — a significant issue for high-density electronic circuits — is not fully understood in such materials. Researchers have now mapped the electrically excited phonon populations and the power dissipation pathways in a working carbon nanotube transistor.