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

Electrical characteristics of Ge pMOSFETs with HfO2, ZrO2, ZrO2/HfO2, and HfZrOxgate dielectrics are studied in this letter. A lower equivalent oxide thickness (EOT) is obtained in ZrO2device, which, however, has a higher interface trap density (Dit) due to its inferior dielectric/Ge interface. Interestingly, the Dit and sub-threshold swing of Ge pMOSFETs are clearly reduced by ZrO2/HfO2stack gate dielectric. A peak hole mobility of 335 cm2/V-s is achieved in ZrO2/HfO2device thanks to good dielectric/Ge interface. Furthermore, the EOT of ZrO2/HfO2device is 0.62 nm, and the leakage current is 2 × 10-3A/cm2. Therefore, a ZrO2/HfO2stack gate dielectric is promising for Ge MOSFETs.