Defect reduction in Si-doped Al0.45Ga0.55N films by SiNx interlayer method
The dislocation density in AlGaN epitaxial layers with Al content as high as 45% grown on sapphire substrates has been effectively reduced by introducing an in-situ deposited SiNx nanomask layer in this study. By closely monitoring the evolution of numerous material properties, such as surface morph...
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Veröffentlicht in: | Journal of applied physics 2014-01, Vol.115 (4) |
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Sprache: | eng |
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Zusammenfassung: | The dislocation density in AlGaN epitaxial layers with Al content as high as 45% grown on sapphire substrates has been effectively reduced by introducing an in-situ deposited SiNx nanomask layer in this study. By closely monitoring the evolution of numerous material properties, such as surface morphology, dislocation density, photoluminescence, strain states, and electron mobility of the Si-Al0.45Ga0.55N layers as the functions of SiNx interlayer growth time, the surface coverage fraction of SiNx is found to be a crucial factor determining the strain states and dislocation density. The dependence of the strain states and the dislocation density on the surface coverage fraction of SiNx nanomask supports the very different growth models of Al-rich AlGaN on SiNx interlayer due to the reduced nucleation selectivity compared with the GaN counterpart. Compared with GaN, which can only nucleate at open pores of SiNx nanomask, Al-rich AlGaN can simultaneously nucleate at both open pores and SiNx covered areas. Dislocations will annihilate at the openings due to the 3D growth initiated on the opening area, while 2D growth mode is preserved on SiNx and the threading dislocations are also preserved. During the following growth process, lateral overgrowth will proceed from the Al0.45Ga0.55N islands on the openings towards the regions covered by SiNx, relaxing the compressive strain and bending the dislocations at the same time. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.4862804 |