Electrical characterization and the strain compensation effect and thermal stability of B-doped heterostructures

Abstract

High-resolution reciprocal lattice mapping (HRRLM) and Hall measurements have been used to characterize the strain, the strain compensation effect, thermal stability and electrical properties of B-doped heterostructures grown at for boron concentrations in the range to and for Ge contents in the range . High-temperature furnace annealing in the range from 500 to was employed. Lattice parameters and lattice distortions in the directions parallel and perpendicular to the growth direction were determined directly as a function of annealing temperature. HRRLM results show that the strain generated in the Si lattice by Ge atoms was partly compensated by B. No broadening around the layer peak was observed for samples for , but for higher B concentrations, for example , a broadening around the layer peak is observed, indicating defects in the layer; this is consistent with transmission electron microscopy micrographs showing (2D) B precipitates on (001) planes. Thermal strain relaxation in layers increased with increasing . For the annealed sample with , a large boron diffusion into the substrate was found by SIMS and for higher boron concentrations, i.e. , 3D boron-related precipitates were observed by transmission electron microscopy. Hall and drift mobilities and their dependence on the strain in B-doped SiGe have also been studied. For strain-compensated samples, which have a low Ge fraction, the Ge atoms give a reduction of both Hall and drift mobilities, while for higher Ge concentrations there is an enhancement of the drift mobility.