Carbon nanotube Schottky diodes have been fabricated in an all-photolithographic process using dissimilar contact metals on high-frequency compatible substrates (quartz and sapphire). Diodes show near-ideal behavior, and rectify currents of up to 100
nA and at frequencies up to 18 GHz. The voltage and frequency dependence is used to estimate the junction capacitance of ~10-18 F and the intrinsic device cut-off frequency of ~400 GHz.
