Texture Evolution in Si/SiC Layered Structures Deposited on Si(001) by Chemical Vapor Deposition
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Texture evolution in SiyySiC layered structures deposited on Si(001) by chemical vapor deposition L-O. Bj¨orketun, L. Hultman, O. Kordina, and J-E. Sundgren Thin Film Physics Division, Department of Physics and Measurement Technology, Link¨oping University, S-581 83 Link¨oping, Sweden (Received 7 April 1997; accepted 24 December 1997)
Texture evolution in SiySiC multilayers deposited by atmospheric pressure chemical vapor deposition on carbonized Si(001) substrates was investigated using x-ray diffraction and transmission electron microscopy. SiC layers were epitaxial and (001)-oriented. Si layers deposited on the SiC exhibited a columnar structure with predominantly (110) orientation which could be related to the nucleation. Orientational relationships were Sif111g k SiCf110g and Sif112g k SiCf110g. Also, a low density of (112)-oriented columns was present. Extensive twinning on the vertical h111j planes within the Si columns led to domains of hexagonal stacking up to 10 nm in size with the presence of 2H-Si and 4H-Si. Subsequent SiC layer growth on the (110)-oriented Si layer resulted in a (110)-oriented SiC layer if the Si layer was carbonized prior to growth. I. INTRODUCTION
There is an increasing interest in studying epitaxial growth of SiC on Si and recently, also, in studying the growth of Si on SiC. Epitaxial Si on 3C-SiC is a candidate material for solving the high contact resistivity problem for wide bandgap 3C-SiC devices.1 The difference in the conduction band position in Si and 3CSiC is reported to be as small as 20.27 eV.2 However, the contact resistivity is still in the 1025 V cm range,3 while the resistivity in the 1027 V cm is preferable from a device application point of view.1 Kim et al. reported that depositing a thin epitaxial Si layer on top of a SiySiC heterojunction diode gives an improved rectification process and increased breakdown voltage from 22 to 25 V.4 Thus, epitaxial Si on 3C-SiC could serve as a contact material for both power devices and high frequency devices.1 The 3C-SiC layer may also serve as a heat sink for Si thin film transistors (TFT).1 Palmour et al.5 considered Si grown on SiC also as a material for improving the quality of passivation oxide layers on SiC. Thermal oxidation of especially p-type SiC (Al doped) results in an oxide layer with incorporated Al (resulting in a high fixed charge in the oxide) and carbon-oxygen compounds.5 By growing a sacrificial Si layer on SiC and subsequently oxidizing the Si layer, an SiO2 oxide virtually free from dopants and carbon-oxygen species is formed.5 If polycrystalline Si layers are used for the sacrificial layer, it is essential to control the texture because the oxidation rate depends on the crystal orientation.6 For the performance of polycrystalline Si devices such as TFT and solar cells, a highly textured Si layer having a large grain size is preferable.7–9 Also, the intragranular defect content as well as the film-to-substrate interface structure affects the device performance.1
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