| The growth rate R of Si(001), Ge(001), and {dollar}rm Sisb{lcub}1-x{rcub}Gesb{lcub}x{rcub}(001){dollar} films deposited on Si(001)2 {dollar}times{dollar} 1 substrates from {dollar}rm Sisb2Hsb6{dollar} and {dollar}rm Gesb2Hsb6{dollar} by gas-source molecular-beam epitaxy (GS-MBE) were determined as a function of temperature T{dollar}sb{lcub}rm s{rcub}{dollar}(300-950{dollar}spcirc{dollar}C) and impingement flux J (0.3-{dollar}7.7times10sp{lcub}16{rcub}{dollar} cm{dollar}sp{lcub}-2{rcub}{dollar} s{dollar}sp{lcub}-1{rcub}{dollar}). R(T{dollar}sb{lcub}rm s{rcub}{dollar},J) curves for Si and Ge films were well described using a model, with no fitting parameters, based upon dissociative chemisorption followed by a series of surface decomposition reactions with the rate-limiting step being first-order hydrogen desorption from the surface monohydride. The hydrogen desorption activation energy for Si and Ge surfaces were found to be 2.04 eV and 1.56 eV, respectively. The zero-coverage reactive sticking probability in the impingement-flux-limited growth regime was found to be 0.036 and 0.052 for {dollar}rm Sisb2Hsb6{dollar} and {dollar}rm Gesb2Hsb6,{dollar} respectively. The growth rate of SiGe alloys R{dollar}sb{lcub}rm SiGe{rcub}{dollar} as a function of the bulk Ge content x was found to be a complex. In the surface-reaction-limited regime, R{dollar}sb{lcub}rm SiGe{rcub}{dollar} increased with Ge surface coverage {dollar}thetasb{lcub}rm Ge{rcub}{dollar} due to the lower activation energy of H{dollar}sb2{dollar} desorption from Ge than from Si. However, in the impingement-flux-limited regime R{dollar}sb{lcub}rm SiGe{rcub}{dollar} decreases with {dollar}thetasb{lcub}rm Ge{rcub}{dollar} due to the lower reactive sticking probability of {dollar}rm Sisb2Hsb6{dollar} on Ge surface sites with respect to on Si sites. The Ge fraction, x1{dollar}sb{lcub}rm Ge{rcub}{dollar}, of SiGe alloys was determined as a function of growth temperature T{dollar}sb{lcub}rm s{rcub}{dollar} and incident flux ratios {dollar}rm Jsb{lcub}Ge2H6{rcub}/Jsb{lcub}Si2H6{rcub}.{dollar} The results were explained by a kinetic model accounting for four simultaneous reaction pathways: reaction of {dollar}rm Sisb2Hsb6{dollar} with Si surface sites, {dollar}rm Sisb2Hsb6{dollar} with Ge sites, {dollar}rm Gesb2Hsb6{dollar} with Si sites, and {dollar}rm Gesb2Hsb6{dollar} with Ge sites. The cross-term reactive sticking probabilities, {dollar}rm Ssbsp{lcub}Ge2H6{rcub}{lcub}Si{rcub}{dollar} and {dollar}rm Ssbsp{lcub}Si2H6{rcub}{lcub}Ge{rcub}{dollar}, were estimated to be 0.33 and {dollar}5.2times10sp{lcub}-3{rcub}{dollar} respectively. |
