ELECTRICAL CHARACTERIZATION AND THE STRAIN COMPENSATION EFFECT AND THERMAL-STABILITY OF B-DOPED SI1-XGEX SI HETEROSTRUCTURES/

High-resolution reciprocal lattice mapping (HRRLM) and Hall measuremen ts have been used to characterize the strain, the strain compensation effect, thermal stability and electrical properties of B-doped Si1-xGe x/Si heterostructures grown at 400 degrees C for boron concentrations in the range 2 x 10(18) cm(-3) to 8 x 10(20) cm(-3) and for Ge content s in the range 0 less than or equal to x less than or equal to 0.23. H igh-temperature furnace annealing in the range from 500 to 1000 degree s C was employed. Lattice parameters and lattice distortions in the di rections parallel and perpendicular to the growth direction were deter mined directly as a function of annealing temperature. HRRLM results s how that the strain generated in the Si lattice by Ge atoms was partly compensated by B. No broadening around the layer peak was observed fo r Si1-xGex samples for C-B < 3 x 10(20) cm(-3), but for higher B conce ntrations, for example C-B = 8 x 10(20) cm(-3), a broadening around th e layer peak is observed, indicating defects in the layer; this is con sistent with transmission electron microscopy micrographs showing (20) B precipitates on (001) planes. Thermal strain relaxation in Si1-xGex layers increased with increasing C-B. For the annealed sample with C- B = 3 x 10(20) cm(-3), a large boron diffusion into the substrate was found by SIMS and for higher boron concentrations, i.e. C-B = 8 x 10(2 0) cm(-3), 3D boron-related precipitates were observed by transmission electron microscopy. Hall and drift mobilities and their dependence o n the strain in B-doped SiGe have also been studied. For strain-compen sated samples, which have a low Ge fraction, the Ge atoms give a reduc tion of both Hall and drift mobilities, while for higher Ge concentrat ions (x > 5%) there is an enhancement of the drift mobility.