Investigation of oxygen and other impurities and their effect on the transparency of a Na flux grown GaN crystal

Mohammed Abo Alreesh, Paul Von Dollen, Thomas F. Malkowski, Tom Mates, Hamad Albrithen, Steven DenBaars, Shuji Nakamura, James S. Speck

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


In this study, we investigate several impurities in bulk GaN crystals grown by the sodium flux technique. In our system, black GaN is in general associated with oxygen, sodium, and molybdenum concentrations in excess of 1019 atoms/cm3. Here, we report on the correlation of high levels of oxygen with opaque crystals. Samples that contain oxygen concentrations above 1019 atoms/cm3 are highly absorbing regardless of the presence of other impurities. Experiments with partially submerged seeds indicated material grown mainly above the nominal liquid surface was more transparent and had a generally lower impurity concentration, especially oxygen. In optically transparent regions, concentrations of oxygen, sodium, and carbon were as low as 7 × 1016, 2 × 1016, and 5 × 1016 atoms/cm3, respectively, while the concentration of molybdenum was below the detection limit.
Original languageEnglish (US)
Pages (from-to)50-57
Number of pages8
JournalJournal of Crystal Growth
StatePublished - Jan 3 2019
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-09
Acknowledgements: This work was supported by the KACST-KAUST-UCSB Solid State Lighting Program (SSLP). The authors acknowledge the use of the Microfluidics Laboratory within the California NanoSystems Institute, supported by the University of California, Santa Barbara and the University of California, Office of the President. The authors acknowledge the use of the MRL Shared Experimental Facilities which are supported by the MRSEC Program of the NSF under Award No. DMR 1720256; a member of the NSF-funded Materials Research Facilities Network (
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • Materials Chemistry
  • Inorganic Chemistry
  • Condensed Matter Physics


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