Information about the local environment of dopants in semiconductor materials is required to understand and help optimize the electrical activity in highly doped samples. The near‐edge (XANES) and extended x‐ray absorption fine structure (EXAFS) components of x‐ray absorption spectra provide detailed information on local geometric and electronic structure about selected atoms. Electron yield and fluorescence detection of As K EXAFS and XANES, with sample rotation to eliminate substrate diffraction, have been used to study the As sites in Si(As) epilayers grown by molecular‐beam epitaxy (MBE) and doped insitu by low‐energy As implantation. Marked differences are found in both the near edge and EXAFS signals between samples prepared under low temperature (460 °C) growth/implantation conditions and those prepared under the preferred, higher temperature (700 °C) growth conditions. The EXAFS analysis indicates that As is located primarily in the substitutional site in the optimal (700 °C) sample but that a large fraction of the As is in a defect site, with possibly some incorporated as some type of As–As clusters in the samples grown at 460 °C.

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