Photocurrent response of the carbon nanotube–silicon heterojunction array

Abstract

A highly ordered array of parallel, identical carbon nanotubes is grown non-lithographically in a bottom-up fabrication approach to form a heterojunction with a silicon substrate. Evidence of a space-charge separated region at the nanotube–silicon interface is present in the form of diode rectification and a closed-circuit zero-bias photocurrent in response to infrared light. Because carbon nanotubes are narrow bandgap semiconductors, their heterojunction with silicon was analysed spectrally via Fourier transform infrared photocurrent spectroscopy with the aim of investigating the suitability of this structure for infrared (IR) detector applications. IR photoresponse shows signs of temperature-dependent activation that is complex but consistent with estimates of the heterojunction barrier height. Considering the many interesting benefits and properties of carbon nanotubes, these results despite their earliness suggest that nanotube–silicon heterojunction systems could form the foundation for a new kind of infrared detection device.