Epitaxy and doping of Si and Si1−xGex at low temperature by rapid thermal chemical vapor deposition

Abstract

Rapid thermal chemical vapor deposition has been applied to the epitaxy and p-type doping of Si and Si1−xGex structure on a 1-nm scale using SiH4, GeH4, and B2H6 in an H2 carrier gas. First, the kinetics of silicon growth is studied between 1000 and 550 °C and the results are shown to be consistent with a model based on the Langmuir–Hinshelwood adsorption mechanism. The growth kinetics of the Si1−xGex alloys is determined down to 525 °C and compared to that of the silicon. Transmission electron microscopy characterizations show that epitaxial structures and short-period (1.7-nm) superlattices without any extended defects are grown at these low temperatures. The boron incorporation in Si and Si1−xGex is then studied. At low temperature, doping levels exceeding 1020 holes cm−3 and delta dopings with a real full width at half-maximum around 1 nm are achieved. In the final part, the growth technique is applied to p-type modulation-doped double heterostructures, and we report a hole mobility value as high as 1800 cm2/V s at 30 K for a sheet density of 4×1012 cm−2.