This study investigated the change in carrier concentration near the surface of a silicon substrate during gallium nitride (GaN) growth with an aluminum nitride (AlN) buffer layer. It was observed that aluminum, gallium, and carbon diffused into the silicon substrate during the growth process and that the carrier concentration increased with increasing concentration of aluminum and gallium impurities. The gallium that diffused into the silicon substrate was identified as having originated from the gallium that decomposed on the reactor wall during the growth process and the gallium introduced onto the silicon substrate during GaN growth. In contrast, the amount of aluminum that diffused into the substrate was influenced by the duration of the trimethylaluminum (TMAl) flow: a long duration of the TMAl flow step before AlN growth led to a high aluminum concentration near the substrate surface.

The workfunction change in doped Si was examined using Kelvin force microscopy in a wide range of doping concentrations from p-type ∼1019 to n-type ∼1020 cm−3 corresponding to the bulk Fermi-level positions from near the valence-band top to conduction-band minimum. Experimental data can be reproduced by model calculations using an appropriate surface-state density composed of the donor- and acceptor-like gap states. These results indicate that no appreciable surface-band bending occurs for doping concentrations less than ∼1014 cm−3 while the bending becomes prominent and the surface Fermi-level is eventually pinned in the midgap region as the concentration increases to ∼1020 cm−3.

Oxygen precipitation properties in the as‐grown defect‐free region of nitrogen‐doped Czochralski silicon (Cz‐Si) single crystals with very low oxygen concentrations ([Oi]) are investigated. At [Oi] values of 4.6–5.9 × 1017 atoms cm−3, oxide precipitates with a high density of 109 cm−3 are generated owing to the enhancement in oxygen precipitation by nitrogen‐doping. In contrast, at [Oi] values of 1.3–2.6 × 1017 atoms cm−3, no oxide precipitates are observed even though the crystals are nitrogen‐doped. Oxygen precipitation in the as‐grown defect‐free region is analyzed based on a thermodynamic model, in which some embryos are assumed to exist in nitrogen‐doped Cz‐Si crystals at high temperatures of crystal growth, and they grow as oxide precipitates during a subsequent cooling process. The analysis of oxygen precipitation indicates that, at [Oi] values below 3 × 1017 atoms cm−3, the radii of oxide precipitates included in the as‐grown Cz‐Si crystals remain small owing to a low growth onset temperature; therefore, oxide precipitates cannot be detected after heat treatment for wafer evaluation. These findings suggest that nitrogen‐doped Cz‐Si crystals with [Oi] values below 3 × 1017 atoms cm−3 are potential materials for power devices, such as insulated gate bipolar transistors.

The segregation gettering mechanism for nickel in p/p + silicon epitaxial wafers is investigated using heavily boron-doped substrates with different resistivities in the range of 7 to 10 m cm. It is found that the segregation gettering becomes active when the nickel contamination level is lower than 1 × 10 13 cm −2 , resulting in the decrease of the nickel precipitation at the surface of epitaxial layers when the resistivity of p + substrates decreases. The gettering model based on the enhanced solubility of nickel in p + substrates could explain the competitive interaction between the segregation effect and the nickel precipitation at the surface below 500 • C during the cooling process after heat treatments. It is suggested by these results that the gettering effect is useful for the low temperature process in the fabrication of a future device.