AVS 45th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM1-WeA

Paper EM1-WeA5
Second Harmonic Study of Ge/Si(100) and Si@sub 1-x@Ge@sub x@(100) Films

Wednesday, November 4, 1998, 3:20 pm, Room 314/315

Session: Si Surface Chemistry
Presenter: P.S. Parkinson, University of Texas, Austin
Authors: P.S. Parkinson, University of Texas, Austin
D.E. Brown, University of Texas, Austin
M.C. Downer, University of Texas, Austin
J.G. Ekerdt, University of Texas, Austin
Correspondent: Click to Email
Second harmonic generation (SHG) allows real-time, in-situ measurement of hydrogen coverage on intrinsic silicon. Thus, SHG has been used by this group to perform hydrogen desorption measurements and growth rate calculations on intrinsic silicon.@footnote 1@ Our current challenge is to develop SHG as a tool to study the Si@sub 1-x@Ge@sub x@(100) alloy surface. We present studies of the SiGe/Si(100) and the Ge/Si(100) systems in vacuum around the E@sub 1@ critical point using SHG. In Ge@sub 2@H@sub 6@ atomic layer epitaxy (ALE) on Si(100), the SH intensity increases linearly with Ge coverage; below 5 ALE cycles (approximately 1.5 ML). Further deposition causes a continuous decrease in the signal intensity and a blue shift in the spectra. Hydrogen passivation of the surface leads to substantial quenching of the signal which reveals the sensitivity of the SH response to the near-surface Ge composition. Monitoring the growth of Si@sub 1-x@Ge@sub x@(100) films, with SHG we observed an initial rise in the SH intensity and then a decrease as the films became rougher and thicker. The time constant for the initial rise became shorter with increasing Ge film composition. Spectra of strained smooth SiGe films showed that the SH intensity at the peak maxima increased with increasing Ge film composition. Also, hydrogen saturation of the film surfaces led to an order of magnitude decrease in the SH response, similar to the Ge/Si(100) system. Thus, the initial rise in SH intensity during growth may correspond to the development of the near-surface Ge composition profile at the leading edge of growth. SH intensity decreased with increasing atomic hydrogen coverages on the SiGe/Si(100) surface; the same trend observed on intrinsic Si(100). Therefore, the SH response to hydrogen coverage in the alloy system might be explainable within the framework of models proposed for the H/Si(100) system.@footnote 2@ @FootnoteText@ @footnote 1@ Xu et al., Appl. Phys. Lett., 71, 1376,(1997). @footnote 2@ Dadap et. al., Phys. Rev. B, 56, 1, (1997).