Characterization of n-channel Si/SiGe modulation doped structures grown by gas source molecular beam epitaxy
We have grown n-channel Si/SiGe modulation doped structures by gas source molecular beam epitaxy using arsine as the n-type dopant source. The structures were characterized by transmission electron microscopy, secondary ion mass spectroscopy, electrochemical capacitance voltage analysis and x-ray diffraction. Arsenic and free electron concentrations in excess of 1019 cm-3 could be obtained with substantial surface segregation. Several different structures have been grown and their transport properties investigated. Low-temperature electron mobilities of up to 60000 cm2 V-1 s-1 in the dark (75800 cm2 V-1 s-1 after illumination) were obtained with a sheet density range (4-7)*1011 cm-2. Parallel conduction is discussed in terms of the effect of illumination.