The Effect of Si and Mg Doping in the Microstructure of Epitaxially Grown GaN


The effect of p- and n-type doping (using Mg and Si, respectively) in the microstructure of GaN, grown epitaxially on (0001)Al2O3 and (111)Si, is studied with X-ray absorption measurements at the N-K-edge. A distortion in the local microstructure around the N atom is detected in the undoped and the Mg doped samples. The N atom is 4-fold coordinated with n Ga atoms in the expected distance and 4-n atoms at a distance longer by 0.28Å, where 2.9 < n < 3.3. Such a distortion, which is attributed to the inward relaxation and the strong interaction between the Ga atoms surrounding the nitrogen vacancies (VN), does not exist in the Si doped sample (carrier concentration=1.57×1018cm−3) where the formation of VN is suppressed due to the n-type doping. However, in GaN:Si the N atom is undercoordinated with 3.3 nearest neighbors instead of 4. This undercoordination indicates the presence of VGa and/or NGa antisite defects. Finally, from the nearest neigbohr distances the lattice parameters were calculated and it is found that although the a and c vary by about 1.5%, the ratio of the lattice constants, c/a, remains constant and equal to 1.63.

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The X-ray absorption measurements were realized with financial support from the EC-HCM (CHGE-CT93-0027) program. One of the authors, T.D.M., acknowledges support from the DARPA agreement MDA 972-95-3-0008.

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Correspondence to M. Katsiktnl.

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Katsiktnl, M., Paloura, E.C., Fieber-Erdmann, M. et al. The Effect of Si and Mg Doping in the Microstructure of Epitaxially Grown GaN. MRS Online Proceedings Library 482, 440–445 (1997).

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