Fig. 1. (Color online) The fabrication process of the high-k/GeO_x/Ge gate stacks with PPO method.

Fig. 2. (Color online) The AR-XPS spectra taken from an 1-nm-thick Al₂O₃/Ge structure with 650 W PPO for 10 s.

Fig. 3. (Color online) (a) The C–V characteristics of an Au/Al₂O₃ (1 nm)/GeO_x (1.2 nm)/Ge MOS capacitor fabricated with the PPO method. (b) The D_it at the Al₂O₃/Ge MOS interfaces w/ and w/o PPO treatment.

Fig. 4. (Color online) The D_it at E_i – 0.2 eV taken from PPO Al₂O₃/GeO_x/Ge MOS interfaces fabricated with different Al₂O₃ capping thickness, plasma power and oxidation time.

Fig. 5. (Color online) (a) The C–V curves of the Au/HfO₂/p-Ge MOS capacitors w/ and w/o PPO, compared with that of Au/Al₂O₃/GeO_x/p-Ge MOS capacitor. (b) The C–V curves of of the Au/HfO₂/Al₂O₃/p-Ge MOS capacitor after PPO. The inset of it shows the energy distribution of D_it of this MOS capacitor.

Fig. 6. The cross section TEM image of an HfO₂ (2.2 nm)/Al₂O₃ (0.2 nm)/Ge structure after 15 s’ PPO using 500 W plasma.

Fig. 7. (Color online) The D_it at the energy of E_i – 0.2 eV of the HfO₂/Al₂O₃/GeO_x/Ge and Al₂O₃/GeO_x/Ge gate stacks, as a function of EOT.

Fig. 8. (Color online) The schematic illusion of the ozone post oxidation process.

Fig. 9. Cross section TEM of an HfO₂ (2 nm)/Al₂O₃ (0.3 nm)/Ge structure after OPO for 60 s at 300 °C.

Fig. 10. (Color online) The EOT of the OPO HfO₂/Al₂O₃/GeO_x/Ge gate stacks with different Al₂O₃ thicknesses and OPO times.

Fig. 11. (Color online) The D_it at the energy of E_i – 0.2 eV in OPO HfO₂/Al₂O₃/GeO_x gate stacks, compared with the PPO gate stacks as a function of EOT.

Fig. 12. (Color online) The oxide thickness of the PPO and OPO gate stacks at side wall and top regions of a 3D structured Ge channel.

Fig. 13. (Color online) The fabrication process of the Ge MOSFETs with OPO HfO₂/Al₂O₃/GeO_x gate stacks.

Fig. 14. (Color online) The I_d–V_d (a) and I_d–V_g (b) characteristics of an (100)/<110> HfO₂/Al₂O₃/GeO_x/Ge pMOSFET fabricated by 60 s OPO.

Fig. 15. (Color online) The hole mobility in HfO₂/Al₂O₃/GeO_x/Ge pMOSFET fabricated by OPO with different oxidation times, compared with that in the HfO₂/Al₂O₃/Ge pMOSFET.

Fig. 16. (Color online) The mechanism of suppressed carrier scattering in the Si passivated GeSn channel, compared with the direct oxide/GeSn channel.

Fig. 17. The cross section TEM image of a GeSn MOS structure having the Si passivation.

Fig. 18. (Color online) (a) I_d–V_g and (b) I_d–V_d characteristics of the (100) GeSn QW pMOSFET with Si passivation.

Fig. 19. (Color online) The hole mobility in the Si passivated GeSn QW pMOSFETs with different channel orientations of (100), (110) and (111).

Fig. 20. (Color online) The comparison of (a) I_d–V_d curves, (b) G_m curves and (c) hole mobility of GeSn QW pMOSFETs with different Sn contents of 2.7%, 4.0% and 7.5%.

Fig. 21. (Color online) The equienergy contours of heavy hole sub-band for GeSn pMOSFETs with different Sn contents of 2.7%, 4.0% and 7.5%, at a N_s of 5 × 10¹² cm^–2. The equienergy contour lines are for multiples of 20 meV.