Effects of native defects on properties of low temperature grown, non-stoichiomtric gallium nitride

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 Ga_N 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. (paper)