The effects of P doping on growth kinetics and surface morphological evolution during Si͑001͒:P gas-source molecular beam epitaxy from Si 2 H 6 and PH 3 at temperatures T s = 500-900°C have been investigated. With increasing PH 3 / Si 2 H 6 flux ratio J P/Si at constant T s , we observe a decrease in the film growth rate R and an increase in the incorporated P concentration C P , both of which tend toward saturation at high flux ratios, which is accompanied by increased surface roughening and pit formation. At constant J P/Si , R increases with increasing T s , while C P initially increases, reaches a maximum at T s = 700°C, and then decreases at higher growth temperatures. We use in situ isotopically tagged D 2 temperature programed desorption ͑TPD͒ to follow changes in film surface composition and dangling bond density db as a function of J P/Si and T s. Measurements are carried out on both as-deposited Si͑001͒:P layers and P-adsorbed Si͑001͒ surfaces revealing ␤ 1 and ␤ 2 peaks due to D 2 desorption from Si monohydride and dihydride species, respectively, as well as the formation of a third peak ␤ 3 corresponding to D 2 desorption from mixed Siu P dimers. Dissociative PH 3 adsorption on Si͑001͒ results in a decrease in db and an initial increase in P surface coverage P with increasing T s. Saturation P values reach a maximum of ϳ1 ML at T s = 550°C, and decrease with T s Ͼ 600°C due to the onset of P 2 desorption. Comparison of P ͑T s ͒ results obtained during film growth with postdeposition C P ͑T s ͒ results reveals the presence of strong P surface segregation. From measurements of P versus C P in Si͑001͒:P layers grown as a function of T s , we obtain a P segregation enthalpy ⌬H s = −0.86 eV. By using the combined set of results, we develop a predictive model for C P versus T s and, J P/Si incorporating the dependence of the PH 3 reactive sticking probability S PH 3 on P , which provides an excellent fit to the experimental data.

The predeposition of P, with coverages θP ranging from 0 to 1 ML, on Si(001) significantly increases both the areal density and spatial self-organization of Ge islands grown by gas-source molecular beam epitaxy from hydride precursors. The Ge island density ρGe initially increases with θP, reaching a maximum of 1.4 × 1010 cm−2 at θP = 0.7 ML, a factor of four times higher than on bare Si(001) under the same deposition conditions, before decreasing at higher P coverages. The increase in ρGe(θP) is due to a corresponding decrease in Ge adatom mean free paths resulting from passivation of surface dangling bonds by adsorbed pentavalent P atoms which, in addition, leads to surface roughening and, therefore, higher Ge coverages at constant Ge2H6 dose. As θP (and hence, ρGe) increases, so does the degree of Ge island ordering along 〈100〉 directions due to the anisotropic strain field surrounding individual islands. Similar results are obtained for Ge island growth on P−doped Si(001) layers where strong P surface segregation provides partial monolayer coverage prior to Ge deposition.