Effects of Surface Orientation on the Performance of Idealized III–V Thin-Body Ballistic n-MOSFETs

Ballistic on-currents of thin-body n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) are compared across group IV (Si, Ge) and III-V (InAs, In_0.5Ga_0.5As, GaAs, GaSb) materials for different body thickness values, surface orientations, and transport directions under several idealization assumptions. Previous simulation studies have shown that, as oxide capacitance increases, typical III-V channels with (100) surface perform worse than Si in the ballistic limit due to the degraded density-of-states (DOS). In this letter, simulation results based on tight-binding band structure calculations verify a recent proposal that confined III-V n-MOSFETs with small Γ-L separations overcome the DOS bottleneck and deliver high injection velocities, boosting on-current performance. By using the quantized L-valleys, GaSb with (100) or (111) surface orientations shows the best ballistic performance, outperforming all other materials. Although GaAs (100) and InAs or In_0.5Ga_0.5As with any surface orientation suffer from the DOS bottleneck, GaAs (111) gives higher ballistic on -currents than Si does.