Low defect ultra-thin fully strained-Ge MOSFET on relaxed Si with high mobility and low band-to-band-tunneling (BTBT)

For the first time, the tradeoffs between higher mobility (smaller bandgap) channel and lower band-to-band-tunneling (BTBT) leakage have been investigated through detailed experiments and simulations. The resulting optimal structure obtained was an ultra-thin, low defect, 2nm fully strained Ge epi channel on relaxed Si, with a 4nm Si cap layer. The fabricated device shows very high mobility enhancements >3.5X over bulk Si devices, 2X mobility enhancement and >10X BTBT reduction over 4nm strained Ge and surface channel 50% strained SiGe devices.