MAGNETOTRANSPORT STUDIES OF SI SIGE AND SI/SIGEC QUANTUM-WELL STRUCTURES GROWN BY MOLECULAR-BEAM EPITAXY AT LOW-TEMPERATURES/

The magneto-transport properties of SiGe and SiGeC quantum well struct ures were studied in relation to their dependence on the growth temper ature, Ge and C concentration, well width, and spacer width. It is fou nd that interface roughness and charged impurities are the main origin s for scattering in SiGe and SiGeC two-dimensional hole gas (2DHG) str uctures. Rapid thermal annealing subsequent to growth improves the mob ility in SiGeC 2DHG by a factor of 2, whereas only a 20% increase is o bserved for SiGe 2DHG. At 1.6 K a mobility of 1930 cm(2)/Vs for Si0.81 Ge0.185C0.05 and 6900 cm(2)/Vs for Si0.85Ge0.15 channels was deduced f rom Shubnikov-de Haas oscillations measured up to 8 T. The effective m ass determined for holes in the SiGeC alloy is 0.21 +/- 0.02. B delta- doped Si layers were used to determine the B diffusion in the temperat ure range from 700 to 850 degrees C by intersubband absorption spectro scopy. (C) 1998 American Vacuum Society.