Analysis of interface trap charges on performance variation in L-shaped tunnel field-effect transistor

The L-shaped tunnel field-effect transistor (LTFET) improves current drivability significantly by transforming the path of the band-to-band tunnelling from point-tunnelling to line-tunnelling, but meanwhile, the gate-source overlapped structure of LTFET brings about a larger active area of interface trap charges (ITCs). In this paper, the impact of ITCs on LTFET's characteristics is investigated in terms of the electric field, dc, analogue/RF, linearity and transient performance. From TCAD simulation results, it is found that for conventional LTFET, different types of ITCs lead to distinct variations in I–V characteristics, subthreshold swing, transconductance, parasitic capacitances, cut-off frequency, linearity parameters such as V IP 2 , V IP 3 , I IP 3 , and I MD 3 and the fall propagation delay ( t pHL ) . To improve the device stability, heterogeneous gate dielectric (HGD) structure is introduced into LTFET. From comparison results, it is found that benefiting from the improved gate controllability near the tunnelling junction, HGD-LTFET not only improves dc, analogue/RF, linearity and transient performance but also effectively suppresses the variation caused by ITCs thus has better stability. Therefore, HGD-LTFET is a very attractive choice in future low-power and high-frequency applications.