Impact of Contact Resistances on Electrical and Thermal Transport in Carbon Nanotube Network Transistors

The breakdown mechanism of carbon nanotube (CNT) networks is explored using a coupled electro-thermal model, which simulates both electrical and thermal transport in CNT network thin film transistors (CN-TFTs). The numerical results are validated against experimental observations on CN-TFTs with similar device geometry, network statistics, and thermal environment. We find the numerical predictions are in good agreement with experimental measurements of power and temperature of CN-TFT devices. Comparing the simulation results with experiments, we observe that the CNT-substrate thermal conductance per unit length is ∼0.1 Wm⁻¹ K⁻¹. This value represents high contact thermal resistance, but is very close to experimental estimations. The thermal profile and breakdown behavior of the CNT network is observed to be more sensitive to CNT-substrate interfacial thermal conductance compared to that of the CNT-CNT interface. The effect of CNT network density on breakdown behavior is also analyzed for relatively low densities of the network. The peak power dissipation in CN-TFTs before breakdown increases with network density, and this peak power is reached at the same source-to-drain bias (V_SD) for all considered densities. The breakdown patterns in CN-TFTs of all considered densities are also observed to have similar characteristics.