Flicker-Noise Improvement in 100-nm $L_{g}\ \hbox{Si}_{0.50}\hbox{Ge}_{0.50}$ Strained Quantum-Well Transistors Using Ultrathin Si Cap Layer

Abstract

This letter presents a record low flicker-noise spectral density in biaxial compressively strained p-channel 100-nm LgSi0.50Ge0.50 quantum-well FETs (QWFETs) with ultrathin Si (~2 nm) barrier layer and 1-nm EOT hafnium silicate gate dielectric. The normalized power spectral density of Id fluctuations (SId/Id 2) in Si0.50Ge0.50 QWFETs exhibits significant improvement by ten times over surface channel unstrained Si pMOSFETs at high Vg due to strong confinement of holes within the high-mobility QW and strong quantization in the ultrathin Si barrier layer enabled by low-thermal-budget device processing. The noise behavior in strained QW devices is found to evolve from being correlated mobility fluctuation dominated across most of Vg range to being Hooge mobility fluctuation dominated at very high Vg.