Numerical Study of a Vertical Tunneling Transistor Based on Gr/BC2N/BC6N and BC2N′/hBN/BC2N′ Heterostructures

We present the results of our computationalstudy onthe electricalcharacteristics of vertical tunneling field-effect transistors (VT-FETs)based on one- and two-dimensional (1D and 2D) configurations of theGr/BC2N/BC6N heterostructure (2D-VT-FET1 andNR-VT-FET1). In a similar set of heterostructure NR-VT-FET1, we replacethe source (Gr) and drain (BC6N) with BC2N & PRIME;and the barrier (BC2N) with hBN (i.e., BC2N & PRIME;/hBN/BC2N & PRIME;), labeled as NR-VT-FET2. To obtain the device characteristics[i.e., I (ON)/I (OFF) ratio, subthreshold swing (SS), and the gate time delay], we employa nonequilibrium Green function formalism with an atomistic tight-binding(TB) approximation. To acquire the TB parameters, we fit the TB bandstructure results to those obtained from the density functional theory.The numerical results show that increasing the number of barrier layersin either set of NR-VT-FETs improves the I (ON)/I (OFF) ratio and SS, degrading the gatedelay. Furthermore, as the ribbon width in the set of VT-FET1 increases,the related I (ON)/I (OFF) ratio decreases. The results also show that, at room temperature,the current modulation as high as & SIM;2.66 x 10(10) (1.72 x 10(9)) is obtained for the NR-VT-FET1(2) whenbiased at 0.5 (0.6) V. These results show remarkable improvementsin comparison with the current modulation obtained from the lateraland vertical tunneling transistors reported earlier. The correspondingSS is as low as 27.63 (25.66) mV/decade. The parameters obtained forthe NR-VT-FET1 satisfy the International Technology Roadmap for Semiconductorsand International Roadmap for Devices and Systems. These VT-FETs canbe suitable for sensor applications due to their low SS.