IOP Publishing, Journal of Physics D: Applied Physics, 38(48), p. 385101, 2015
DOI: 10.1088/0022-3727/48/38/385101
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The properties of GaN thin films grown by molecular beam epitaxy at temperatures from 80 to 500 °C under a wide range of Ga:N flux ratios are studied. We found that at growth temperatures as low as ~80 °C, GaN films still have a polycrystalline, columnar morphology with c-axis preferred orientation. Soft x-ray absorption and emission and optical absorption measurements on Ga-rich samples suggest the presence of a partially occupied GaN antisite defect band located at ~1.2 eV below the conduction band minimum. P-type conductivity observed in this LTMBE Ga-rich GaN is consistent with transport within this partially occupied defect band.