Characterization of n-channel Si/SiGe modulation doped structures grown by gas source molecular beam epitaxy

Abstract

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 10 19 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 cm 2 V -1 s -1 in the dark (75800 cm 2 V -1 s -1 after illumination) were obtained with a sheet density range (4-7)*10 11 cm -2. Parallel conduction is discussed in terms of the effect of illumination.