Triangular-channel Ge NFETs on Si with (111) sidewall-enhanced Ion and nearly defect-free channels

Abstract

Due to the highest electron mobility (2200 cm²/Vs) on (111) Ge surface, the n-channel triangular Ge gate-all-around (GAA) FET with (111) sidewalls on Si and L_g=350 nm shows 2x enhanced I_on of 110 μA/μm at 1V with respect to the devices with near (110) sidewalls. A novel process to etch away the defective Ge near Ge/Si interface from epitaxial Ge grown on SOI achieves a nearly defect-free channel, good gate control triangular gate, and larger effective width. Electrostatic control of SS= 94 mV/dec (at 1V) can be further improved if superior gate stack than EOT= 5.5 nm and D_it= 1×10¹² cm^-2eV^-1 is used. The I_on can be further enhanced if the line edge roughness (LER) can be reduced. The Ge GAA n-FET is reported for the first time with CMOS compatible process, which makes the circuits integration much easier.