Impact of growth conditions on intrinsic carbon doping in GaN layers and its effect on blue and yellow luminescence

In this study, the GaN films were deposited in the multilayered structures under different growth conditions. SIMS analysis showed that intrinsic carbon incorporation around two orders can be controlled effectively by varying the growth parameters. Defects analysis by cross-sectional cathodoluminescence (X-CL) is demonstrated as a useful analytical technique for unambiguously understanding the effect of incorporation of the intrinsic carbon concentration on the yellow luminescence (YL) and blue luminescence (BL) band intensities. It was inferred from the experimental data that the observed BL and YL intensities are due to the electronic transitions through the isolated C_N and C_NO_N complex, respectively. This finding is in contrast to the theoretically published literature that two charged states of C_N are responsible for both BL and YL which sought that the BL emission to be always smaller in comparison to YL emission. Our experimental data, for all different growth conditions showed the prominent BL in comparison to YL except for the growth at sufficiently lower temperature which is considered to be more conducive for higher oxygen incorporation into the stoichiometry. This increases the probability of C_NO_N formation which is manifested in the enhancement of YL intensity over BL as the formation energy of C_NO_N complex is lower than the C_N defect. Thus, X-CL analysis method can be key to address the challenges of understanding the impurity character in multi-thin layered GaN structures.