Impact of strain and Ge concentration on the performance of planar SiGe band-to-band-tunneling transistors

Compressively strained Si
_1-x
Ge
_x
band-to-band tunneling field effect transistors with planar structure and HfO
₂
/TiN gate stack have been produced and analyzed, with different Germanium concentrations of x = 0.35, 0.50 and 0.65. Simulations using a nonlocal band-to-band-tunneling model have been carried out to understand the switching behavior and its dependence on the material parameters. One would expect an increase of the tunneling currents for the increase of x. However, the Si
_0.5
Ge
_0.5
devices show the highest I
_on
and smallest S, whereas Si
_0.35
Ge
_0.65
devices exhibit decreased currents due to partial strain relaxation.