AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP28
Surfactant Behaviors of Bi and As in the Growth of Ge/Si(001)-2x1 Systems Studied with Photoemission Spectroscopy

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: P. De Padova, Consiglio Nazionale delle Ricerche, Italy
Authors: P. De Padova, Consiglio Nazionale delle Ricerche, Italy
R. Larciprete, ENEA, Italy
C. Quaresima, Consiglio Nazionale delle Ricerche, Italy
A. Reginelli, Consiglio Nazionale delle Ricerche, Italy
S. Priori, Consiglio Nazionale delle Ricerche, Italy
E. Paparazzo, Consiglio Nazionale delle Ricerche, Italy
L. Moretto, Consiglio Nazionale delle Ricerche, Italy
P. Perfetti, Consiglio Nazionale delle Ricerche, Italy
Correspondent: Click to Email
Heteroepitaxial Ge/Si(001)-2x1 systems show promising applications in the fabrication of infrared detectors. A layer-by-layer growth is essential for smooth films to be obtained, and this is greatly facilitated by addition of surfactant elements, such as As, Bi and Sb. Among these, Bi is a good candidate, as it little affects the Ge chemistry and has a low desorption temperature, whereas As has been generally regarded as being the ideal surfactant element. We used synchrotron radiation (SR) photoemission and XPS techniques to comparatively study the roles that Bi and As play in the growth of thin and thick Ge films on Si substrates. Angle-resolved SR core level spectra allowed us to identify two distinct growth modes in Ge/Bi/Si(001) systems as a function of Ge coverage. Sub-monolayer Ge coverages involve Ge- and Bi-atoms exchanging sites with each other, whereas greater Ge coverages involve the Ge-atoms lying both underneath Bi-atoms, as well as on top of the Si substrate. XPS depth-profiling conducted into a 15-monolayer Ge-film reveals that the Bi-atoms remain confined to the true surface. SR spectra of the Ge/As/Si(001) system show that the As-atoms lie anchored to the Si substrate, even for great Ge coverages, which is at striking variance with the expected layer-by-layer growth. Ge growth, carried out via codeposition of As and Ge on Si substrates, gives spectral evidences suggestive of the As atoms diffusing downward the Ge film, with no Ge-As site exchange taking place. We discuss our results in light of theoretical and experimental reports available in the literature, and propose an interpretation to account for the different surfactant behaviors of Bi and As.