Self-Consistent Subband Structure and Mobility of Two Dimensional Holes in Strained SiGe MOSFETs

The motivation to research strained SiGe layers on relaxed silicon is to enhance the very low hole mobility observed in conventional Si MOSFETs. This is mainly due to large hole effective masses and strong surface roughness scattering. In this work, the buried SiGe quantum well, chosen as the active channel for carrier transport, enhances mobility in two ways. First, the carriers are confined in the SiGe well and are removed from the Si-SiO₂ interface, so interface roughness is not a big factor. Secondly, strained SiGe has a lower hole effective mass than unstrained Si and the mobility is expected to increase as the Ge concentration increases. We present the results of a self-consistent subband structure and low field mobility calculations for holes in a Si-SiGe heterostructure FET. Our results are in agreement with the experimental work by Garone and coworkers, indicating the validity of our model.