Carbon nanotube-silicon heterojunction arrays and infrared photocurrent responses

We study and demonstrate a periodic array of carbon nanotube-silicon heterojunctions, its functioning as an infrared (IR) detector, and report on the first observation of near- to mid-IR photocurrent response in both the cooled and uncooled modes. The formation of carbon nanotubes in a periodic dense array, parallel to each other and perpendicular to the silicon substrate, offers a new promising IR material platform with spectral tunability and scalability in field size and absorbance as well as uniform electrical and optical accesses to each of the nanotubes. The spectral dependence of the photocurrent also allows for an estimate of the band gap of the nanotubes, which is found to be in good agreement with that determined from thermally activated dark conductivity measurements.