Trapping Behaviors in CNTFETs: Measurement and Analysis of Time Constant, Energy Level, and Trap Location Based on Transient Drain Current

The trapping behaviors in the carbon nanotube field-effect transistor (CNTFET) pose a major challenge to the operation stability. Herein, a trap characterization system based on the transient drain current is constructed to realize the comprehensive measurement and analysis of trap levels in the CNTFET with SiO2 as the gate oxide. A Bayesian deconvolution function is developed to optimize the trap extraction accuracy based on the measured transient current, and three electron traps and three hole traps are identified under the positive and negative gate stress, respectively. Leveraging this model, a comprehensive experimental and theoretical analysis of the trap information, including the time constant, exact amplitude, and energy levels, can be conducted. In particular, the charge trapping mechanisms under different gate and drain biases are studied based on the dependence of trap amplitudes on filling voltages. Through these advances, we analyze the physical origin and specific location of each trap and compare the trap properties against a wide range of trap levels reported in previous studies. The approach used in this study can be potentially beneficial to better understand the trap levels responsible for the hysteresis issues and optimize the performance and reliability of the CNTFET.