High field breakdown of carbon nanotube network transistors

We develop and employ a self-consistent electro-thermal model to study the high field breakdown of carbon nanotube (CNT) network thin film transistors (CN-TFTs). We investigate the effects of the CNT alignment angle and length distribution on the breakdown process caused by excessive self-heating. We examine relevant breakdown characteristics such as the peak current and corresponding voltage and power in relation to these two network parameters. We find that the breakdown behavior can significantly vary with respect to the CNT length and alignment distribution even when the network density is kept the same. Results suggest that an optimum alignment (∼ 65°) can be found for a network with constant CNT lengths to obtain higher current/power without setting off an early breakdown. When both CNT length and alignment angle are varied, we find that networks with higher average CNT length have lower optimum alignment such that doubling the average CNT length lowers the optimum alignment angle by half. Therefore these network parameters need to be carefully selected to achieve greater thermal reliability and higher electrical performance.