Self-Organized Ge Nanospherical Gate/SiO2/Si0.15Ge0.85-Nanosheet n-FETs Featuring High ON-OFF Drain Current Ratio

Abstract

We reported experimental fabrication and characterization of Si0.15Ge0.85 n-MOSFETs comprising a gate-stacking heterostructure of Ge-nanospherical gate/SiO2/Si0.15Ge0.85-nanosheet on SOI (100) substrate in a self-organization approach. This unique gate-stacking heterostructure is simultaneously produced in a single oxidation step as a consequence of an exquisitely controlled dynamic balance between the concentrations of oxygen, Si, and Ge interstitials at 900 degrees C. Process-controlled tunability of nanospherical gate of 60-100 nm in diameter, gate oxide thickness of 3 nm, and Si0.15Ge0.85 nanosheet with compressive strain of -2.5% was achieved. Superior gate modulation is evidenced by subthreshold slope of 150 mV/dec and I-ON/I-OFF > 5 x 10(8) (I-OFF < 10(-6) mu A/mu m and I-ON > 500 mu A/mu m) measured at V-G = + 1V, V-D = + 1 V, and T = 80 K for our device with channel length of 75 nm.