STUDY ON SMALL-SIGNAL IMPEDANCE OF SINGLE-WALLED ZIGZAG CARBON NANOTUBES IN TERAHERTZ FREQUENCY REGIME

We theoretically study the static and dynamic transport properties of Mott-Gurney diodes based on semiconducting single-walled zigzag carbon nanotubes (CNTs). The electric field and velocity distribution of the diode under dc voltage is obtained by solving the steady-state drift-diffusion equations, which involve the negative differential velocity. The current-voltage characteristic of CNT diode exhibits a distinctive positive differential resistance. The high-frequency impedance is calculated with the small-signal analysis method. A major feature of the proposed CNT diode is that the bias-and tube index-dependent impedance show several negative windows in terahertz frequency range despite the positivity of the dc differential resistance. This property makes the CNT-based Mott-Gurney diode a promising candidate for the generation and amplification of terahertz signals within the desired frequency region.