Local microstructures of Si in GaN studied by X-ray absorption spectroscopy

Z.H. Lu, Department of Metallurgy and Materials Science University of Toronto, Toronto, ON M5S 3E4

T. Tyliszczak, P. Brodersen and A.P. Hitchcock, Institute for Materials Research McMaster University, Hamilton, Ont., Canada L8S 4M1

J.B. Webb, H. Tang, and J. Bardwell, Institute for Microstructural Sciences National Research Council Canada Ottawa, Canada, K1A 0R6

Si K-edge X-ray absorption spectroscopy (XAFS) has been used to study the local structure of Si dopant in GaN crystalline material. Doping concentrations from 8.0x10^16 to 4.4x10^19 cm^(-3) were investigated. It is observed that near-edge spectra vary significantly as a function of doping concentration. At low dopant concentrations, Si K-edge spectra exhibit features resembling those obtained from N K-edge measurement, while the near-edge spectra of high Si-dopant concentration samples are more similar to that of Si3N4. Dopant concentration dependant changes in near-edge spectra are explained as due to formation of various types of Si clusters. A Si-induced strain-field near the surface is proposed as the main force for cluster formation during epitaxial growth. Si K-edge extended XAFS spectra support conclusions derived from the near edge spectra.

PCSA codes: 81.60. Cp, 78.70.Dm, 68.35.-p