Germanium MOSFETs for Nanoelectronics

Abstract

Ge is a promising channel material for nanoscale MOSFETs due to its high mobility, which translates into higher drive current and smaller gate delay. However, for Ge to become main-stream, surface passivation and heterogeneous integration of crystalline Ge layers on Si must be achieved. We have demonstrated growth of fully-relaxed smooth single crystal Ge layers on Si using a novel multi-step growth and hydrogen anneal process without any graded buffer SiGe layer. Surface passivation of Ge has been achieved with its native oxynitride and high-k metal oxides of Al, Zr and Hf. High mobility p-MOSFETs have been demonstrated in bulk Ge with these gate dielectrics and metal gates. However, due to its smaller bandgap Ge suffers from large leakage currents. We present novel, Si and Ge based heterostructure MOSFETs, which significantly reduce the leakage while retaining high mobility, making them suitable for scaling into the sub-20nm regime.