Electrically active and inactive B lattice sites in ultrahighly B doped Si(001): An x-ray near-edge absorption fine-structure and high-resolution diffraction study

B lattice positions are determined as a function of B concentration C-B in ultrahighly doped Si(001):B layers grown by gas-source molecular beam epita xy from B2H6/Si2H6 For C-B less than or equal to 2.5 c 10(20) cm(-3), all B atoms reside on tetrahedrally bonded electrically active substitutional Si sites. At higher C-B, inactive B is incorporated as B pairs located on sin gle Si sites and oriented primarily along in-plane [100] and [010] directio ns. The B pairs are sp(2) bonded with trigonal coordination while substitut ional single B atoms are sp(3). A surface reaction path leading to inactive B incorporation is proposed. [S0031-9007(99)09265-0].