HETEROSTRUCTURE SI1-XGEX CHANNEL PMOSFETS WITH GE CONCENTRATION

Simultaneous numerical solution of Schrodinger's and Poisson's equatio ns is used to show that a narrow triangular Ge composition profile gra ded to a peak value of 100% with rise and fall lengths of just 2 nm ca n provide very effective subsurface hole confinement in a heterostruct ure Si1-xGex channel p metal-oxide-semiconductor field effect transist or (pMOSFET). This result is confirmed by analysis of MOS capacitor C- V curves for experimental devices fabricated using a very low thermal budget process on substrates grown by ultrahigh vacuum chemical vapor deposition, Unfortunately. transconductance measurements on experiment al ion-channel MOSFETs indicate that the peak low-field mobility of ho les in the buried channel is just 132 cm(2) V-1 s(-1). slightly lower than that for a typical surface channel Si MOSFET. Buried channel hole mobilities up to 262 cm(2) V-1 s(-1) were obtained for reference devi ces fabricated using the same process with more conventional wide tria ngular composition profiles graded to a peak Ge content of 40%. (C) 19 98 American Vacuum Society. [S0734-2101(98)03902-5].