High-Mobility TaN/ $\hbox {Al}_{2}\hbox {O}_{3}$ /Ge(111) n-MOSFETs With RTO-Grown Passivation Layer

We report the fabrication of high-electron-mobility Ge(III) n-MOSFETs using a novel and simple approach to passivate a Ge surface by rapid thermal oxidation (RTO). A thin interfacial GeO₂ layer is formed by RTO, which passivates the high-k/Ge interface. The GeO₂-passivated n-MOSFETs fabricated using a gate-first self-aligned process with high-k/metal gate demonstrate a high peak effective mobility (μ_eff ~ 713 cm² · V^-1 · s^-1) with ~2x enhancement over control Si(100) devices. Moreover, at a drain bias of 1 V and at a gate overdrive of 1.2 V, Ge MOSFETs (L ~ 75 μm) show a drive current of ~1.1 mA/ mm, which is ~1.6 X higher than that of the control Si devices. In addition, a good subthreshold slope of ~130 mV/decade and an Jon/-Toff ratio ~10³ were achieved using the GeO₂ interfacial layer formed by RTO.