Wet-chemical passivation of Si(111)- and Si(100)-substrates

The influence of preparation-induced surface roughness, as well as the hydrogen and oxide coverage on electronic properties of Si(111) and Si(100) surfaces was investigated by combining various surface-sensitive techniques. Simultaneous surface photovoltage (SPV) and spectroscopic ellipsometry (SE) measurements, both in the ultraviolet/visible (UV–VIS) and the infrared (IR) spectroscopic region, yielded detailed information about intrinsic and extrinsic surface states on hydrogen (H)-terminated Si(111) and Si(100) surfaces, immediately after the wet-chemical preparation as well as during the initial oxidation. The energetic distributions of interface states Dit(E) on Si(100) and Si(111) surfaces were correlated to the surface roughness 〈dr〉, the change of hydrogen coverage and the oxide growth on an atomic scale. As shown by these experiments, generally higher interface state densities Dit, min were observed on Si(100) surfaces in comparison to Si(111). However, on Si(100) substrates a faster oxide growth and a significantly thicker final native oxide layer were found. The wet-chemical preparation methods of hydrogen or oxide passivated surfaces on Si(100) substrates were carefully optimized, resulting in smooth H-terminated surfaces (〈dr〉≈4 Å and Dit, min<5×1010 cm−2 eV−1) and passivating oxide layers in the thickness range of 1–3 nm (Dit, min <5×1011 eV−1 cm−2).