Radiofrequency transistors based on aligned carbon nanotube arrays

The development of next-generation wireless communication technology requires integrated radiofrequency devices capable of operating at frequencies greater than 90 GHz. Carbon nanotube field-effect transistors are promising for such applications, but key performance metrics, including operating frequency, at present fall below theoretical predictions. Here we report radiofrequency transistors based on high-purity carbon nanotube arrays that are fabricated using a double-dispersion sorting and binary liquid interface aligning process. The nanotube arrays exhibit a density of approximately 120 nanotubes per micrometre, a maximum carrier mobility of 1,580 cm2 V−1 s−1 and a saturation velocity of up to 3.0 × 107 cm s−1. The resulting field-effect transistors offer high d.c. performance (on-state current of 1.92 mA µm−1 and peak transconductance of 1.40 mS μm−1 at a bias of −0.9 V) for operation at millimetre-wave and terahertz frequencies. Transistors with a 50 nm gate length show current-gain and power-gain cutoff frequencies of up to 540 and 306 GHz, respectively, and radiofrequency amplifiers can exhibit a high power gain (23.2 dB) and inherent linearity (31.2 dBm output power of the third-order intercept point) in the K-band (18 GHz). Transistors based on arrays of aligned carbon nanotubes can exhibit cutoff frequencies of up to 540 GHz, and could be further scaled for operation at millimetre-wave and terahertz frequencies.