title: Length scaling of carbon nanotube electric and photo diodes down to sub-50 nm.
abstract: Carbon nanotubes (CNTs) are promising candidates for future optoelectronics and logic circuits.1-3 Sub-10 nm channel length CNT transistors have been demonstrated with superb performance.4 Yet, the scaling of CNT p-n diodes or photodiodes, basic elements for most optoelectronic devices, is held back on a scale of micrometers.5-8 Here, we demonstrate that CNT diodes fabricated via a dopant-free technique show good rectifying characteristics and photovoltaic response even when the channel length is scaled to sub-50 nm. By making a trade-off between performance and size, a diode with both channel length and contact width around 100 nm, fabricated on a CNT with a small diameter (d ∼ 1.2 nm), shows a photovoltage of 0.24 V and a fill factor of up to 60%. Study on the dependence of turn-on voltage on scaled channel length reveals transferred charges induced potential barrier at the contact in long channel diodes and the effect of self-adjusting charge distribution. This effect could be utilized for realizing stable and high performance sub-100 nm pitch CNT diodes. As elementary building blocks, such tiny electric and photodiodes could be used in nanoscale rectifiers, photodetectors, light sources, and high-efficiency photovoltaic devices.
authors.affiliation: Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University , Beijing 100871, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Xu
authors.forename: Sheng
authors.initials: S
authors.lastname: Wang
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Lian-Mao
authors.initials: LM
authors.lastname: Peng
keywords: carbon nanotube; diode; nanophotonics; photodiode