A new system for sodium flux growth of bulk GaN. Part II: in situ investigation of growth processes
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AbstractWe report recent results of bulk GaN crystal growth using the sodium flux method in a new crucible-free growth system. We observed a (0001) Ga face (+c-plane) growth rate >50 µm/h for growth at a N2 overpressure of ~5 MPa and 860 °C, which is the highest crystal growth rate reported for this technique to date. Omega X-ray rocking curve (ω-XRC) measurements indicated the presence of multiple grains, though full width at half maximum (FWHM) values for individual peaks were <100 arcseconds. Oxygen impurity concentrations as measured by secondary ion mass spectroscopy (SIMS) were >1020 atoms/cm3. By monitoring the nitrogen pressure decay over the course of the crystal growth, we developed an in situ method that correlates gas phase changes with precipitation of GaN from the sodium-gallium melt. Based on this analysis, the growth rate may have actually been as high as 90 µm/h, as it would suggest GaN growth ceased prior to the end of the run. We also observed gas phase behavior identified as likely characteristic of GaN polynucleation.
CitationVon Dollen P, Pimputkar S, Alreesh MA, Nakamura S, Speck JS (2016) A new system for sodium flux growth of bulk GaN. Part II: in situ investigation of growth processes. Journal of Crystal Growth 456: 67–72. Available: http://dx.doi.org/10.1016/j.jcrysgro.2016.08.018.
SponsorsThanks to Guy Patterson and Doug Rehn for help with many aspects of equipment design and fabrication. Thanks to Dr. Tom Mates for performing the SIMS measurements and to Steven Griffiths and Thomas Malkowski for many helpful conversations and insights. The authors acknowledge the support from the Solid State Lighting and Display/Energy Center at, University of California, Santa Barbara and the Materials Research Laboratory (MRL) Central Facilities, which are supported by the MRSEC Program of the NSF under Award no. DMR 1121053; a member of the NSF-funded Materials Research Facilities Network (www.mrfn.org). This work was supported by the KACST-KAUST-UCSB Solid State Lighting Program.
JournalJournal of Crystal Growth
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