The effects of Ge content in poly-Si1-xGex gate material on the tunneling barrier in PMOS devices

The use of SiGe gates in MOSFET technology has promise as a single-gate mat erial for both n- and p-channel MOSFETs. The Ge content in the gate, howeve r, affects the gate energy band diagram. While Ge in the SiGe gate does not affect the conduction-band energy level, it is found to raise the valence- band energy level and reduce the gate bandgap. This change results in an in crease in the gate current resulting mainly from the tunneling of electrons from the valence band of the gate in PMOSFETs. This paper reports on the e ffects of Ge content in SiGe gates on the tunneling characteristics of PMOS FETs.