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8 March 2014 Point defect management in GaN by Fermi-level control during growth
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A point defect control scheme is demonstrated, to control point defects during the growth of doped wide bandgap semiconductors. First the theoretical description of this new concept is presented, second GaN:Mg is used as a model system and as an experimental example to show its feasibility. It can be shown that above bandgap UV-light illumination during the growth can reduce the passivation and compensation of Mg acceptors in GaN:Mg. The amount of hydrogen impurities, that usually passivates Mg at doping concentrations around Mg:2x1019 cm-3, is significantly reduced by UVillumination. The resistivity of samples grown with UV is similar to the resistivity of post-growth annealed samples. No post growth annealing was needed. In contrast samples that are doped below Mg:<1x1018 cm-3 become n-type conductive when the samples are grown with UV illumination. This observation suggests a reduced incorporation of Mg acceptors due to the UV light. At low Mg doping concentrations the native donor incorporation by O donors dominates the conductivity over Mg acceptors. UV-illumination therefore reduces compensation of donors by Mg acceptors. Thus, these observations support the concept of UV illumination as a way to control the Fermi level of different charged point defects to control compensation in doped semiconductors.
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Marc P. Hoffmann, James Tweedie, Ronny Kirste, Zachary Bryan, Isaac Bryan, Michael Gerhold, Zlatko Sitar, and Ramón Collazo "Point defect management in GaN by Fermi-level control during growth", Proc. SPIE 8986, Gallium Nitride Materials and Devices IX, 89860T (8 March 2014);


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