Lattice strain from holes in heavily doped Si:Ga

Heavily doped Si:Ga has been prepared by liquid phase epitaxy (LPE) and by ion-implantation with rapid thermal annealing (RTA) or laser annealing (LA). Peak substitutional Ga concentrations obtained by each technique were 1.5, 2.5 and 2.9 x 1020 cm-3, respectively. Substitutional fractions (> 90%) were similar in the three types of substitutional Ga atom in Si of +0.9 ± 0.1 x 10-24 cm3/atom was measured by double crystal x-ray diffraction. The average nearest neighbor Si-Ga bond length measured with extended x-ray absorption fine structure (EXAFS) was 0.237 ± 0.004 nm, indistinguishable, to within experimental error, from the intrinsic Si-Si bond length, 0.235 nm, indistinguishable, to within experimental error, from the intrinsic Si-Si bond length, 0.235 nm. Combining these two results the lattice strain per hole in the Si valence band was calculated, +0.4 ± 0.8 x 10-24 cm3. This result complements the lattice contraction per electron in the Si conduction band (-1.8 ± 0.4 x 10-24 cm3) already reported for Si:As. 15 refs., 4 figs., 1 tab