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Deep level transient spectroscopy in plasma-assisted molecular beam epitaxy grown Al 0.2 Ga 0.8 N / GaN interface and the rapid thermal annealing effectThe incorporation of deep level defects in n-type GaN grown by ammonia-based molecular beam epitaxy ͑MBE͒ is studied via systematic adjustment of the NH 3 / Ga flux ratio. Deep level optical and transient spectroscopies, which together enable deep level detection throughout the GaN bandgap, reveal defect states whose individual concentrations vary with the NH 3 / Ga flux ratio. A general trend of lower concentration for deep levels at E C − 3.28, E C − 1.28, E C − 0.62, and E C − 0.25 eV with higher NH 3 / Ga flux ratio was observed, with the strongest reduction at the E C − 0.25 eV level, consistent with expectations for a V N -related defect. The known C N impurity state at E C − 3.28 eV and suspected C I -related state at E C − 1.28 eV also showed a moderate decrease in concentration at the higher NH 3 / Ga flux ratio. In contrast, the V Ga -related defect at E C − 2.62 eV was insensitive to the NH 3 / Ga flux ratio over the range studied here. Taken together, ammonia-MBE GaN has deep level defects with different sensitivities in flux ratios suggestive of independent physical sources. However, the total trap concentrations were significantly reduced for higher NH 3 / Ga flux ratios in n-type GaN grown by ammonia-MBE under the range of growth conditions used in this study, suggesting that higher NH 3 / Ga flux ratios will generate higher electronic quality GaN material when using ammonia-based MBE for device applications.

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