Browsing by Author "Jang, LY"

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Gallium K-edge EXAFS study of GaN : Mg films
(2000)
Pan, YC
;
Wang, SF
;
Lee, WH
;
Lin, WC
;
Shu, CK
Ga K-edge extended X-ray absorption fine structure (EXAFS) measurement was employed to investigate the local structure of GaN:Mg films grown by metalorganic vapor phase epitaxy (MOVPE) with various Cp,Mg dopant flow rates using both in-plane and out-of-plane polarization modes of X-ray. The near edge absorption spectra were found to depend on X-ray polarization strongly for undoped GaN sample and weakly to minutely for heavily Mg-doped and amorphous films. The results indicate Mg incorporation modifies the local structure around the absorber Ga atom and, hence, alters the molecular orbital electron transition of GaN sample. EXAFS analysis showed both vacancy and Mg-interstitial defects contribute to the reduction of coordination numbers along the hexagonal c-axis of GaN:Mg film.
Gallium K-edge x-ray absorption study on Mg-doped GaN
(2001-01-01)
Pan, YC
;
Wang, SF
;
Lee, WH
;
Lee, MC
;
Chen, WK
Ga K-edge x-ray absorption measurements were employed to investigate Mg-doping effects in GaN samples. Strong polarization-dependent x-ray absorption near-edge structures become less pronounced with increasing doping concentration, indicating the formation of a mixing-phase structure of cubic and hexagonal phases. Analysis of the extended x-ray absorption region of the spectra revealed doping-related defects such as vacancies, substitutions, and interstitial occupations. They were formed anisotropically in the crystal c axis direction and its perpendiculars. Disorderliness arising from phase mix and defects is believed to have lowered the Debye temperature of the doped GaN films and caused the destructive interference of the absorption fine-structure oscillation functions. These effects were taken into account for the observed large coordination number reductions in our samples. (C) 2001 American Institute of Physics.