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A GaN bulk crystal with improved structural quality grown by the ammonothermal method

Nature Materials volume 6, pages 568–571 (2007)Cite this article

Abstract

The realization of high-performance optoelectronic devices, based on GaN and other nitride semiconductors, requires the existence of a high-quality substrate. Non-polar or semipolar substrates have recently been proven to provide superior optical devices to those on conventional c-plane substrates1,2,3,4. Bulk GaN growth enables GaN substrates sliced along various favourable crystal orientations. Ammonothermal growth is an attractive method for bulk GaN growth owing to its potential to grow GaN ingots at low cost. Here we report on improvement in the structural quality of GaN grown by the ammonothermal method. The threading dislocation densities estimated by plan-view transmission electron microscopy observations were less than 1×106 cm−2 for the Ga face and 1×107 cm−2 for the N face. No dislocation generation at the interface was observed on the Ga face, although a few defects were generated at the interface on the N face. The improvement in the structural quality, together with the previous report on growth rate5 and scalability6, demonstrates the commercial feasibility of the ammonothermal GaN growth.

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Figure 1: Cross-sectional scanning electron micrograph of GaN grown for 50 days.
Figure 2: Cross-sectional TEM images of the GaN crystal grown by the ammonothermal method.
Figure 3: Nomarski microscope images for the grown surface after H3PO4 etching at 160 ∘C.

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Acknowledgements

The authors acknowledge F. Orito, K. Fujito and M. Saito at Mitsubishi Chemical Corporation for supplying HVPE-grown free-standing GaN substrates.

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  1. Materials Department, University of California, Santa Barbara, California 93106-5050, USA

  2. ERATO/JST UCSB group, University of California, Santa Barbara, California 93106-5050, USA

Authors and Affiliations

  1. Tadao Hashimoto

Authors
  1. Tadao Hashimoto
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  2. Feng Wu
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  3. James S. Speck
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  4. Shuji Nakamura
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Contributions

F.W. carried out the TEM characterization. J.S.S. and F.W. provided interpretation of structural characterization and fruitful discussions. S.N. directed the research.

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Correspondence to Tadao Hashimoto.

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The authors declare no competing financial interests.

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Hashimoto, T., Wu, F., Speck, J. et al. A GaN bulk crystal with improved structural quality grown by the ammonothermal method. Nature Mater 6, 568–571 (2007). https://doi.org/10.1038/nmat1955

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