Influence of surface reconstruction on the orientation of homoepitaxial silicon films

Abstract

Single-crystal silicon films grown at 400°C on Si(l 1 l):B(V3x V5) are rotated 180° about the surface normal with respect to the substrate. We discuss a mechanism based on chemical effects due to the boron (VJx VJ) reconstruction that favors the film to grow with a ZMype (twin) orientation. Films grown on the SiCl 1 l)-(7x7) reconstruction under identical conditions have the ^-type (untwinned) orientation. PACS numbers: 68.35.Bs, 61.16.Di, 68.35.DvIn all prior cases of homoepitaxy, the epilayer has been crystallographically aligned with the substrate, irrespective of the surface reconstruction, impurity segregation, or other effects at the substrate surface. The original surface reconstruction has always reordered into an unreconstructed interface between the substrate and film, since epitaxy requires a sufficiently high temperature for surface diffusion to occur. Here, we describe Si homoepitaxial growth on the boron VJxVJ surface of SiC111) with j monolayer of boron. At low temperature, the surface reconstruction is partly preserved, buried under an epilayer, and the homoepitaxial layer grows rotated by 180° with respect to the substrate. Tung et al. x have demonstrated rotated heteroepitaxial films. We will use their notation; if the substrate orientation is denoted as "^-type," the "ZMype" orientation corresponds to a layer rotated by 180° about the normal (111) direction.To our knowledge this is the first example of homoepitaxial growth with the overlayer not crystallographically aligned with the substrate. We show experimentally that this phenomenon is critically sensitive to the presence of boron at the original interface during growth, although after growth boron may be in-diffused with no change in film orientation. Modeling suggests that strain effects cannot account for this phenomena. We suggest that the stabilization of the twin boundary interface is related to chemical (electronic) effects which favor a wurtzite stacking at the VJxVJ interface.Samples were prepared in a molecular-beam-epitaxy (MBE) chamber equipped with a quartz-crystal thickness monitor, an electron-gun evaporator to deposit silicon, and a Knudsen cell to deposit boron from HBO2. Low-energy electron diffraction (LEED) and Auger analysis were performed in situ, and x-ray diffraction, transmission electron microscopy (TEM), Rutherford backscattering spectroscopy, nuclear reaction analysis, and Hall-effect measurements were done after removing samples from the MBE chamber. Surfaces were prepared by chemical growth of a thin protective oxide layer before transferring into the vacuum system. The boron VJxVJ surface reconstruction was prepared either by surface segregation of y monolayer (ML) of boron from boron-implanted samples at 900-1000°C, or by deposition of boron onto /?-type samples from HBO2 while the sample was held at 750°C. The surface structure thus formed is unique to the SiCl 11)/B system since boron occupies a subsurface site in a fivefold-coordinated substitutional site under a silicon adatom. 2 " 4 Silicon films of 350...

The thermal dissociation of decaborane on Si(111)-(7×7) and doping effects in the near surface region

“…By depositing additional silicon on top of this structure, a highly boron-doped internal layer (1/3 monolayer or 7x10 2 1 cm -3 ) can be confined to the atomic-dimension in thickness [7][8][9][10]. But because a high temperature is necessary to produce the well-ordered (-V3xV3)R30° surface structure in the first place, the thermal diffusion of boron into bulk silicon thus overlayer.…”

Formation of multiple nanoscale twin boundaries that emit intense light in indirect-gap AlGaAs epilayers

“…Such twin boundaries are formed at dissolution pits [23], that can be formed on AlGaAs substrates by the annealing without an As atmosphere, even though it is not clear how much rough or how many As-deficient the substrate. Excess Al and Ga atoms, as well as residual oxygen atoms, can agglomerate in the dissolution pits, and they might act as the catalyst for the growth of twin boundaries [23], similar to boron atoms on a silicon substrate [24]. It is considered that the orientation of twin boundaries distributes unisotropically due to the difference of the growth rates on different atomic planes [22], and the growth rate of f1 1 1g A differs from that of f1 1 1g B for AlGaAs [10].…”

S.T.M. studies on semiconductor surfaces and metal-semiconductor interfaces

“…Strain effects resulting in an assymetric clamping of the sample can produce a larger step density at the surface as shown in figure 6. The influence of strain effects on the surface step density could thus be evidenced although no figure 5, results in Ag clustering and the grey scale picture of figure 7 shwos that the Ag clusters are mostly aligned along the terraces of around 500 Â width and that the characteristic cluster size is of the order of the terraces width. On a similar system at higher coverages we have studied local photon emission, as it has been proposed by Gimzewski [2] …”

“…This is namely the B/Si(lll) B/3 xv'3 R(30° [5]. The more energetically favourable situation with B atoms in a sublayer substitutional position [6] thus constituting a deltadoped layer confers a remarkable stability to this substrate with interesting properties regarding metal or semiconductor epitaxy [7]. Our first data on Cu deposits on this substrate indicates that the presence of B at the surface changes drastically the surface chemistry when compared to the 7 x 7 Si(lll) substrate [8].…”