Atomic surface structure of Si(100) substrates prepared in a chemical vapor environment

摘要

Subsequent III-V integration by metal-organic vapor phase epitaxy (MOVPE) or chemical vapor deposition (CVD) necessitates elaborate preparation of Si(100) substrates in chemical vapor environments characterized by the presence of hydrogen used as process gas and of various precursor molecules. The atomic structure of Si(100) surfaces prepared in a MOVPE reactor was investigated by low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) available through a dedicated, contamination-free sample transfer to ultra high vacuum (UHV). Since the substrate misorientation has a fundamental impact on the atomic surface structure, we selected a representative set consisting of Si( 100) with 0.1 °, 2° and 6° off-cut in [011 ] direction for our study. Similar to standard UHV preparation, the LEED and STM results of the CVD-prepared Si(l 00) surfaces indicated two-domain (2 × 1)/(1 × 2) reconstructions for lower misorientations implying a predominance of single-layer steps undesirable for subsequent III-V layers. However, double-layer steps developed on 6° misoriented Si(100) substrates, but STM also showed odd-numbered step heights and LEED confirmed the presence of minority surface reconstruction domains. Strongly depending on misorientation, the STM images revealed complex step structures correlated to the relative dimer orientation on the terraces.