High-frequency performance of submicrometer transistors that use aligned arrays of single-walled carbon nanotubes
The unique electronic properties of single-walled carbon nanotubes (SWNTs) make them promising candidates for next generation electronics, particularly in systems that demand high frequency (e.g., radio frequency, RF) operation. Transistors that incorporate perfectly aligned, parallel arrays of SWNTs avoid the practical limitations of devices that use individual tubes, and they also enable comprehensive experimental and theoretical evaluation of the intrinsic properties. Thus, devices consisting of arrays represent a practical route to use of SWNTs for RF devices and circuits. The results presented here reveal many aspects of device operation in such array layouts, including full compatibility with conventional small signal models of RF response. Submicrometer channel length devices show unity current gain (ft) and unity power gain frequencies (fmax) as high as ∼5 and ∼9 GHz, respectively, with measured scattering parameters (S-parameters) that agree quantitatively with calculation. The small signal models of the devices provide the essential intrinsic parameters: saturation velocities of 1.2 × 107 cm/s and intrinsic values of ft of ∼30 GHz for a gate length of 700 nm, increasing with decreasing length. The results provide clear insights into the challenges and opportunities of SWNT arrays for applications in RF electronics.