Improved Electrical Characteristics of Ge pMOSFETs With ZrO2/HfO2Stack Gate Dielectric

Abstract

Electrical characteristics of Ge pMOSFETs with HfO2, ZrO2, ZrO2/HfO2, and HfZrO x gate dielectrics are studied in this letter. A lower equivalent oxide thickness (EOT) is obtained in ZrO2 device, which, however, has a higher interface trap density ( $\text{D}_{\mathrm { {it}}})$ due to its inferior dielectric/Ge interface. Interestingly, the $\text{D}_{\mathrm {{it}}}$ and sub-threshold swing of Ge pMOSFETs are clearly reduced by ZrO2/HfO2 stack gate dielectric. A peak hole mobility of 335 cm+ $^{{{2}}}$ /V-s is achieved in ZrO2/HfO2 device thanks to good dielectric/Ge interface. Furthermore, the EOT of ZrO2/HfO2 device is 0.62 nm, and the leakage current is $2\times 10^{{ {-3}}}$ A/cm $^{{{2}}}$ . Therefore, a ZrO2/HfO2 stack gate dielectric is promising for Ge MOSFETs.