Ge N-Channel MOSFETs with ZrO₂ Dielectric Achieving Improved Mobility

High-mobility Ge nMOSFETs with ZrO₂ gate dielectric are demonstrated and compared against transistors with different interfacial properties of ozone (O₃) treatment, O₃ post-treatment and without O₃ treatment. It is found that with O₃ treatment, the Ge nMOSFETs with ZrO₂ dielectric having a EOT of 0.83 nm obtain a peak effective electron mobility (μ_eff) of 682 cm²/Vs, which is higher than that of the Si universal mobility at the medium inversion charge density (Q_inv). On the other hand, the O₃ post-treatment with Al₂O₃ interfacial layer can provide dramatically enhanced-μ_eff, achieving about 50% μ_eff improvement as compared to the Si universal mobility at medium Q_inv of 5 × 10¹² cm^-2. These results indicate the potential utilization of ZrO₂ dielectric in high-performance Ge nMOSFETs.