Effect of Body Thickness on the Electrical Performance of Ballistic n-Channel GaSb Double-Gate Ultrathin-Body Transistor

We investigated the effect of body thickness on the electrical performance of GaSb double-gate ultrathin-body (DG-UTB) MOSFET by examining the band structure of the 12- (~2 nm), 24- (~4 nm), 36- (~6 nm), and 48- (~8 nm) atomic-layer (AL) thick GaSb. Two different surface orientations, namely, (100) and (111), were studied. sp³d⁵s^* tight-binding model is used to calculate the band structures of GaSb MOSFET. Ballistic transport was studied using the semiclassical top-of-barrier model with applied self-consistent real-space potential across the body. First, we found that for (100) surface orientation, GaSb DG-UTB FET with body thickness of 24 ALs offered relatively larger ON-state current for various gate dielectric materials studied. However, for (111) surface orientation, 12 ALs GaSb DG-UTB FET showed the best performance due to its reasonably higher injection velocity and larger electron density. Furthermore, for the FET with a body thickness of 48 ALs and HfO₂ dielectric, it was observed that the charge occupations shift toward the surface, unlike the cases of FETs with thinner body, leading to the formation of inversion charge on the surface. Finally, we compared the ON-state current of GaSb DG-UTB FET with different channel surface orientations and found that (100) surface generally outperforms (111) surface in terms of ON-state current.