Understanding and Physical Modeling Superior Hot-Carrier Reliability of Ge pNWFETs

Hot-carrier degradation (HCD) of Ge pNWFETs has been shown to be significantly lower and different than that of Si pNWFETs. Here we accurately model degradation and the time-to-failure (TTF) measured during HC stress in Ge pNWFETs. For this, we use our HCD framework validated against hot-carrier degradation in Si devices, and first we show here that it thoroughly represents HCD Si pNWFETs. This framework is naturally extendable to incorporate new defects (O-vacancies) and their precursors (Ge-O bonds) which are involved in HCD in Ge transistors. These Ge-O bonds are present due to segregation of Ge through the Si cap into the SiO
₂
film of the high-k gate stack with subsequent formation of the SiGe/Si
_x
Ge
_y
O
_2(x
+
y)
interface. The Ge-H bonds are argued to be unstable while a low concentration of Si-H bonds with a broad distribution of the bonding energy should still be considered. Our unified model has been demonstrated to accurately capture degradation and TTFs in both Ge and Si pNWFETs, with the superior slope of the TTF vs. drain current dependency in the Ge devices determined by the defect creation energetics, hereby supported by ab initio calculations.