Desorption of Arsenic Species during the Surfactant Enhanced Growth of Ge on Si(100)

Abstract

The desorption and scattering of As 4 and As 2 species from the surface during the growth of germanium films on Si(100) with continuous As 4 deposition is monitored using laser ionization time-of-flight mass spectrometry. A significant increase in the flux of As 2 from the surface is observed when the Ge flux is admitted to the surface. Upon discontinuation of the germanium growth process, the As 4 and As 2 signal levels remain at this increased level. A comprehensive study of the desorption fluxes of As 4 , As 2 , and As species from both Ge (100) and Si(100) substrates was performed as a function of substrate temperature and incident As 4 flux to determine the kinetics of desorption of the different species from the substrates. The behavior of the As 2 desorbed fluxes as a function of surface temperature is qualitatively different on the Ge(100) and Si(100) substrates.The results indicate that the catalytic cracking of As 4 to As 2 is more effective on Ge(100) compared to Si(100) at substrate temperatures between 800 and 1000 K, most likely because of more rapid desorption of As 2 at a given temperature on Ge(100). A phenomenological activation energy for the desorption of As atoms from Ge(100) of 1.2 ( 0.4 eV is also obtained. The implications for the surfactant enhanced growth of Ge on Si(100) are discussed.

Arsenic surface segregation during in situ doped silicon and Si1−xGex molecular beam epitaxy

“…The steadystate surface arsenic fraction is maintained by a balance of three fluxes: the incoming source flux, desorption, and incorporation into the epilayer. While the incoming flux is the same in the two cases, the desorption rate from germanium atoms is greater because the As-Ge bond is weaker than the As-Si bond [19]. Furthermore, arsenic incorporation is also enhanced in Si 1Àx Ge x .…”