Effects of high B-doping on Si(001) dangling bond densities, H desorption and film growth kinetics during gas-source molecular beam epitaxy

Abstract

Si(001) layers doped with B concentrations C B ranging from 5 × 10 16 to 2 × 10 21cm −3 were grown on Si(001)-(2 × 1) substrates by gas-source molecular beam epitaxy using Si 2H 6 and B 2H 6. B was incorporated into substitutional electrically active sites at concentrations up to 2.5 × 10 20cm −3. With increasing incident flux ratios J B 2H 6 /J Si 2H 6 ≥ 0.01 (corresponding to C B = 2 × 10 19cm −3), film growth rates decreased at T s ≥ 600°C, but increased at T s ≤ 550°C. Deuterium temperature-programmed desorption measurements as a function of increasing C B show strong B surface segregation, decreased steady-state H coverages θ H, and lower dangling bond densities. The Si:B growth kinetics are well described by a model showing that at low temperatures, where steady-state θ H values are high, increased H desorption rates from B-backbonded Si adatoms dominate, leading to an enhancement in R Si, whereas at higher temperatures R Si decreases due to the decreased adsorption-site density.