Schottky Barriers in Carbon Nanotube Heterojunctions

Electronic properties of heterojunctions between metallic and semiconducting single-wall carbon nanotubes are investigated. Ineffective screening of the long-range Coulomb interaction in one-dimensional nanotube systems drastically modifies the charge transfer phenomena compared to conventional semiconductor heterostructures. The length of depletion region varies over a wide range sensitively depending on the doping strength. The Schottky barrier gives rise to an asymmetry of the $I-V$ characteristics of heterojunctions, in agreement with recent experimental results by Yao et al. and Fuhrer et al. Dynamic charge buildup near the junction results in a steplike growth of the current at reverse bias.