Comparison of deep level incorporation in ammonia and rf-plasma assisted molecular beam epitaxy n-GaN films

The use of rf-plasma and ammonia nitrogen sources for growth of GaN films by molecular beam epitaxy (MBE) are compared in terms. of defect incorporation using deep level. optical spectroscopy (DLOS). and deep level transient spectroscopy (DLTS). To better improve the understanding of ammonia-based MBE growth of GaN and potential defect sources as opposed to the more studied plasma source-based MBE-grown, material several V/III ratios were also investigated, which were generated via systematic adjustment of the ammonia flow rates during growth. The DLOS spectra, comparing deep traps within the n-GaN grown using N-plasma and ammonia sources, reveal the presence of the same deep levels due tok background carbon and gallium vacancies, with energy levels at EC-3.28, EC-2.62, and EC-1.28. The DLTS results of the N-plasma and ammonia-based MBE samples show two similarly dominant electron traps at EC-0.60, and EC-0.24 in each sample. Measurements made as a function of V/III flux ratio for ammonia-based MBE growth indicate a large dependence of the EC-0.24 eV trap concentration on growth flux ratio, which is significant for guiding continued optimization of this promising MBE growth method for GaN devices.