Effective Electrical Passivation of Ge(100) for HfO2Gate Dielectric Layers Using O2Plasma

The O2plasma pretreatment was investigated for passivation for HfO2high-kGe metal-oxide-semiconductor devices. With proper in situ O2plasma passivation, the capacitance–voltage hysteresis was substantially reduced from ∼900 to ∼50 mV for the HfO2/Ge gate stacks. Capacitors show well-behaved capacitance–voltage characteristics on both p- and n-type Ge substrates, indicating an efficient electrical passivation of the Ge interface. The interface trap density for both types of Ge substrates after passivation is below 4 × 1011eV−1cm−2. A leakage current density of 1.5 × 10−7and 2.1 × 10−8A/cm2was obtained for the HfO2/p-Ge and HfO2/n-Ge capacitor with equivalent oxide thickness of 1.8 nm at VFB± 1 V, respectively.