We present a low energy electron diffraction (LEED) study of the initial stages of epitaxial growth of silicon on silicon with emphasis on the growth mechanisms involved. Silicon is evaporated under ultrahigh vacuum conditions. We used pulsed laser irradiation and thermal annealing for surface preparation and show that epitaxial growth can take place on surfaces, prepared by either procedure. We determined the epitaxial temperature (defined with electron diffraction) for Si(111) and Si(100) substrates. We also used 4.0° vicinal oriented Si(111) to determine the influence of a large number of misorientation steps on the growth mechanism. The (100) epitaxial temperature equals 470 K, much lower than that of Si(111) which is found to be 870 K. The use of vicinal (111) surfaces lowers the epitaxial temperature to 770 K. Pulsed laser irradiation was not only used to prepare clean and ordered substrate surfaces, but also as a means to prepare the metastable Si(111) surface, exhibiting a (1×1) LEED pattern. The initial stages of epitaxial growth on this surface were studied. Room temperature depositions of Si on Si(100) are shown to be partly ordered. Three differently prepared (100) substrates were used to determine the influence of substrate surface preparation on the structure of the overlayer.

Si overlayers have been grown under ultrahigh vacuum conditions on GaP(100) single crystals by means of molecular beam epitaxy. For growth temperatures of 300 °C and higher (2×1) low-energy electron diffraction patterns of the Si overlayers were seen at all overlayer thicknesses produced (8–10 000 Å). By means of Auger electron spectroscopy segregation of P and Ga on top of the grown Si surface was measured. With Rutherford backscattering using ion channeling we found Si minimum channeling yields of 3% in the GaP:Si(100) heterostructures, which corresponds well to the yield of pure monocrystalline (100) Si. Two methods are described to eliminate the Ga and P segregation.

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Modulation doped silicon structures have been grown using ultra-highvacuum molecular beam epitaxy (MBE) and ion implantation sequentially. Silicon (100) samples were implanted with As, Ga and B, after which they were introduced in a Si-MBE apparatus. We used conventional thermal annealing (sometimes combined with ion sputtering) as well as pulsed laser irradiation to remove the implantation damage and to prepare substrate surfaces in such a way that epitaxial growth can be achieved. Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) were used to monitor surface conditions prior to growth. Epitaxial layers of thicknesses of 200-1000 Å were grown in ultrahigh vacuum conditions. LEED analysis of the epitaxial layer surface showed that the layer structural quality is improving as a result of epitaxial growth (this was confirmed with Rutherford backscattering and channeling). By repeating the implantation-growth cycle several times, i.e. implanting the MBE-grown samples and growing another epitaxial overlayer on top, modulation doped structures were formed. On a number of these structures electrical measurements were performed to characterize layer quality. We compare substrate surface conditions (structural, composition), growth conditions and the results of electrical measurements and RBS/channeling in order to understand the growth mechanisms involved and to optimize the conditions to manufacture advanced silicon devices