N atomic-layer doping in a nanometer-order Si/Si1-xGex/Si(100) heterostructure using ultraclean low-pressure chemical vapor deposition and its thermal stability at 650 degrees C were investigated. In the Si0.5Ge0.5 epitaxial layer, it is found that a N doping dose of 6 x 10(14) cm(-2) can be confined within an about 1.5 nm-thick region even after 650 degrees C heat treatment in contrast to the result for Si cap layer growth on the thermally nitrided Si(100) with a N doping dose of 6 x 10(14) cm(-2) which was found to be amorphous. Moreover, it is suggested that the confined N atoms in Si1-xGex preferentially form Si-N bonds and that formation Of Si3N4 is enhanced by the heat treatment at 650 degrees C. (C) 2009 Elsevier B.V. All rights reserved.