Infrared Response of Stacked GeSn Transistors

To detect the existence of the parasitic channel of GAAFET for the advanced technology nodes, a non-destructively optical method is investigated. With the infrared illumination at the wavelength of 1310 nm, 1550 nm, and 2000 nm, the main infrared responses of the stacked Ge
_0.91
Sn
_0.09
channels and the parasitic Ge
_0.94
Si
_0.06
channel are ΔV
_T
and I
_ph
, respectively. In addition, the photoresponses between the floating channels with the parasitic channel underneath and the transistors with the sole parasitic channel distinct from each other were observed. By distinguishing the optical responses under infrared illumination, the existence of the parasitic channel can be checked non-destructively.