Comparison of Charge Pumping and $1/f$ Noise in Irradiated Ge pMOSFETs

Irradiated Ge pMOSFETs have been characterized via charge pumping $(I_{\rm CP})$ and $1/f$ noise. The noise increases much more with irradiation than does $I_{\rm CP}$ for devices with eight Si monolayers at the interface, while devices with five Si monolayers and lower halo implantation dose exhibit comparable increases in noise and $I_{\rm CP}$ with irradiation. These results suggest that border traps in the ${\rm HfO}_{2}$ affect the noise more than interface traps, and that devices with eight Si monolayers have a higher border-trap density than devices with five Si monolayers. Noise measurements as a function of gate voltage show that the border trap density increases significantly toward the Ge valence band edge, while three-level charge pumping reveals an interface trap density that increases slightly toward midgap.