Design and Modeling of Line-Tunneling Field-Effect Transistors Using Low-Bandgap Semiconductors

Effects of Source Doping Profile on Device Characteristics of Lateral and Vertical Tunnel Field-Effect Transistors

“…However, the current-voltage characteristics of the lateral and vertical TFETs are almost identical in the subthreshold regions. Because the onset of the lateral tunneling is more premature than that of the vertical tunneling [19], the lateral tunneling dominates the subthreshold region, whereas the vertical tunneling mainly contributes to the on-state current in the vertical TFET. Figure 3 plots the energy-band diagrams at off-and on-states to explain the working principles of the lateral and vertical TFETs.…”

“…Electrons tunnel vertically from the source center to the source surface before swept toward the drain. Because the tunneling in the vertical TFET occurs within the heavily-doped source, the tunnel width is smaller and the tunnel area is larger than those in the lateral TFET [13,19]. Therefore, the on-current is significantly enhanced in the vertical TFET device.…”

“…Generally, a higher source concentration results in a stronger band bending at the depletion region of tunnel junction. Therefore, the tunnel barrier width is narrower and the on-off transition of the tunnel barrier is more abrupt to produce the higher on-current and smaller subthreshold swing in heavier source TFETs regardless of their lateral or vertical structure [6,16,19]. However, a comprehensive comparison of source concentration effects on the device characteristics in lateral and vertical TFETs has not been reported adequately in the scientific literature.…”

“…A doped n + drain of 5×10 18 cm -3 and a 100 nm n-channel of 10 17 cm -3 were fixed to minimize the ambipolar current [8], whereas the source doping concentration and gradient are appropriately varied for study purposes. In the vertical TFETs, the gate fully overlaps the channel with a gate-source overlap length of 50 nm to maximize the on-current [19].…”

A new analytical threshold voltage model of cylindrical gate tunnel FET (CG-TFET)

“…But on the contrary it results low drain current due to the tunneling of charge carriers at the source-channel interface based on non-local Band-to-Band tunneling (BTBT) phenomena [7][8][9][10]. However a number of techniques such as bandgap engineering, gate engineering, use of compound semiconductors, use of high-k dielectric have been employed to improve the drain current in TFET structure [11][12][13][14]. Similarly different TFET models based on multi-gate structure have been developed in recent times, to improve the device performance and scaling capability [15][16][17].…”