Conduction band discontinuity and electron mobility in a strained Si/SiGe heterostructure

High-quality n-type modulation doped Si/SiGe heterostructures have been fabricated by rapid thermal chemical vapor deposition and electrically characterized by Hall effect measurements from room temperature (RT) to 2 K. The conduction band discontinuity between the strained Si channel and the relaxed Si0.67Ge0.33 overlayer has been experimentally determined (ΔEc = 290 ± 30 meV). Furthermore, a new technique for the direct measurement of the RT-mobility of confined electrons in the Si channel is presented. It consists in chemically etching the doped SiGe overlayer, thus reducing its contribution to the transport properties of the structures. Interpretation of the Hall data has been made using the two-carrier type Hall model and shows that a RT-electron mobility of 2150 cm2/Vs is systematically obtained in the strained Si channel.