High-Mobility Modulation-Doped Graded Sige-Channel P-Mosfet's

We report the successful fabrication and operation of the first modulation-doped SiGe-channel p-MOSFET's, A novel device design consisting of a graded SiGe channel, an n+ polysilicon gate, and p+ modulation doping is used. The boron-doped layer is placed underneath the undoped SiGe channel to achieve the desired threshold voltage without degrading the mobility. The low-field hole mobility for a channel graded from 25% to 15% germanium is 220 cm2/V – s at 300 K and increases to 980 cm2/V – s at 82 K. © 1991 IEEE