RELATION BETWEEN ELECTRICAL ACTIVATION AND THE B-INDUCED STRAIN IN SIDETERMINED BY RECIPROCAL LATTICE MAPPING

Boron-induced strain in Si epilayers was characterized by using high-r esolution x-ray reciprocal lattice mapping, Samples grown by molecular beam epitaxy with high crystalline quality and full electrical activa tion of dopants with concentrations f rom 2 x 10(19) cm-3 up to almost -equal-to 1 X 10(21) cm-3 were employed, with measured lattice mismatc hes up to almost-equal-to 0.5% (tetragonal strain almost-equal-to 1%). The measured lattice contraction coefficient, was (5.6 +/- 0.1) X 10( -24) cm3/atom, by considering the ratio of the lattice mismatch to the total dopant concentration. However, by considering only the effectiv ely incorporated and activated dopant concentration, given by the meas ured carrier concentration, beta was found to be (6.3 +/- 0.1) x 10(-2 4) cm3/atom. Further measurements on B-doped structures grown at high temperatures (greater-than-or-equal-to 600-degrees-C), which had only partial electrical activation (< 20%), confirmed that the B-induced la ttice contraction in Si is related not to the total dopant concentrati on, but rather to the carrier concentration, which in principle corres ponds to the active and substitutionally incorporated dopants. The hig h accuracy of our strain measurements was facilitated by the reciproca l lattice mapping method. In-plane and normal components (relative to the sample surface) of the lattice parameter of the epilayers were mea sured independently, and minute variations in the strain/relaxation st atus of the structures were accounted for.