B incorporation and hole transport in fully strained heteroepitaxial Si1 − xGex grown on Si(0 0 1) by gas-source MBE from Si2H6, Ge2H6, and B2H6

Abstract

B-doped Si 0.95 Ge 0.05 (0 0 1) films were grown on Si(0 0 1) by gas-source molecular beam epitaxy in the surface-reaction-limited regime using Si 2 H 6 , Ge 2 H 6 , and B 2 H 6 . Incorporated B concentrations C B (5 × 10 16 − 3 × 10 19 cm −3 ) were found to increase linearly with increasing B 2 H 6 flux J B 2 H 6 (6 × 10 12 −2 × 10 15 cm −2 s −1 ) at constant film growth temperature T s , and to decrease exponentially with 1/ T s at constant J B 2 H 6 . The B 2 H 6 reactive sticking probability ranged from ⋍ 3.3 × 10 −4 at T s = 600°C to 8.2 × 10 −4 at 700°C and film growth rates were independent of J B 2 H 6 . Structural analysis by in-situ reflection high-energy electron diffraction combined with post-deposition high-resolution plan-view and cross-sectional transmission electron microscopy, high-resolution X-ray diffraction, and reciprocal lattice mapping showed that all films were fully strained, with measured relaxations less than the detection limit, ⋍ 3 × 10 −5 , and exhibited no evidence of dislocations or other extended defects. Room-temperature Si 0.95 Ge 0.05 : B conductivity mobilities were equal to theoretical values and a factor of ⋍ 2 higher than corresponding results for bulk Si. μ c varied from 410 cm 2 V −1 s −1 with C B = 5 × 10 16 cm −3 to 60 cm 2 V −1 s −1 with C B = 3 × 10 19 cm −3 .