Analyses and optimization of strained-SiGe on Si pMOSFETs by using full-band device simulation

Transport properties of strained-SiGe on Si channel pMOSFETs is analyzed in detail by full-band device simulation. Although injection velocity (nu_inj) of SiGe devices can be significantly enhanced over Si (100%@Ge-content chi_Ge = 0.7), I_on enhancement factor for short-channel SiGe devices is much smaller (40%) than expected from nu_inj. Careful examination revealed that this is due to anomalous reduction of injection carrier density caused by the lower density-of-states (DOS). To increase short-channel saturation I_on, higher chi_Ge is desirable because of the higher nu_inj, though too high chi_Ge reduces critical SiGe thickness, thereby degrading the low field mobility. Additional uniaxial <110> strain is very effective for boosting SiGe device performance, because it increases v_inj without decreasing the DOS.