High-mobility TaN/Al₂O₃ /Ge(111) n-MOSFETs with RTO-grown passivation layer

We report the fabrication of high-electron-mobility Ge(111) 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-κ /Ge interface. The GeO₂-passivated n-MOSFETs fabricated using a gate-first self-aligned process with high-κ/metal gate demonstrate a high peak effective mobility (μ_eff∼713cm²ċV^-1ċ ^-1 with ∼2× 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∼75μm) show a drive current of ∼1.1 mA/mm, which is ∼1.6× higher than that of the control Si devices. In addition, a good subthreshold slope of ∼130 mV/decade and an I_ON/I_OFF ratio ∼10₃ were achieved using the GeO₂ interfacial layer formed by RTO.