Facet growth of self-separated GaN layers through HVPE on large square-patterned template

Highlights

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Square-patterned template with large periodicity was designed for self-separated GaN freestanding substrate by HVPE.
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Graphical surface and mixed polarity was formed which regularly distributed according with underneath template pattern.
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The growth on large square template is a facet growth mode.
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The lateral strain distribution within GaN surface by Raman is well interpreted on the basis of facet growth mode.

Abstract

A self-separated GaN layer was prepared by hydride vapor phase epitaxy (HVPE) on a square-patterned template with large periodicity. Self-separation was completed by breakage of the fragile layer because of the thermal stresses generated during the cooling process after HVPE growth. The GaN layer exhibited graphical surface comprising the terrace and the concave, the shapes of which were corresponding with the mask pattern. The terrace came from the growth on window openings, and had Ga-polarity by wet etching and micro-Raman measurement. The concave over the mask was composed of large inclined facets, and was demonstrated to have N-polarity. The growth on large square-patterned template was considered to be facet growth. The polarity inversion was related to dislocation accumulation. The strain distribution regularly varied, which was interpreted based on the facet growth mode.

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