Quantitative Characterization of Fast-Trap Behaviors in Al2O3/GeOx/Ge pMOSFETs

In this paper, fast trap behaviors in Ge pMOSFETs with Al
₂
O
₃
/GeO
_x
/Ge gate-stack are evaluated and quantitatively characterized using a novel sub-1-ns ultrafast measurement (UFM) system. By changing the operation temperature and the rising time of the applied gate voltage (V
_g
), it is found that the fast trap filling process could be observed within the first 10 ns after the gate voltage was applied, and the process would be more clearly characterized at a raised operation temperature. In addition, the trap density distribution and the time constant of the fast traps inside the valence band edge are experimentally extracted based on the UFMs. It is found that the trap densities inside the valence band edge are within the range of 10
¹³
to 10
¹⁴
cm
^-2
· eV
^-1
, which are consistent with the reported values from the Hall measurements. It is experimentally confirmed that the time constants of the fast traps in Ge pMOSFETs with Al
₂
O
₃
/GeO
_x
/Ge gate-stack are about 10 ns, and deeper energy level corresponds to smaller time constant.