Si(001):B gas-source molecular-beam epitaxy: Boron surface segregation and its effect on film growth kinetics

B-doped Si~001! films, with concentrations CB up to 1.7310 22 cm, were grown by gas-source molecular-beam epitaxy from Si2H6 and B2H6 at Ts5500– 800 °C. D2 temperature-programed desorption ~TPD! spectra were then used to determine B coverages uB as a function of CB and Ts . In these measurements, as-deposited films were flash heated to desorb surface hydrogen, cooled, and exposed to atomic deuterium until saturation coverage. Strong B surface segregation was observed with surface-to-bulk B concentration ratios ranging up to 1200. TPD spectra exhibited b2 and b1 peaks associated with dideuteride and monodeuteride desorption as well as lower-temperature B-induced peaks b2* and b1* . Increasing uB increased the area under b2* and b1* at the expense of b2 and b1 and decreased the total D coverage uD . The TPD results were used to determine the B segregation enthalpy, 20.53 eV, and to explain and model the effects of high B coverages on Si~001! growth kinetics. Film deposition rates R increase by >50% with increasing CB.̃1310 19 cm at Ts<550 °C, due primarily to increased H desorption rates from B-backbonded Si adatoms, and decrease by corresponding amounts at Ts>600 °C due to decreased adsorption site densities. At Ts>700 °C, high B coverages also induce $113% facetting. © 1997 American Institute of Physics. @S0021-8979~97!03216-7#