Gallium Nitride (GaN) is one of the most promising wide band gap semiconductor materials that are replacing silicon (Si) in power electronic applications. However, the quality of the material is limiting its application in high performance power electronic materials. Apart from the threading dislocations reported in our previous studies [1, 2], some area defects are observed in both ammonothermal GaN substrates by synchrotron X-ray topography (XRT) (Figure 1). Information on the nature of these defects is important to prevent the formation of such defects and improve the crystal quality.

In this study, synchrotron X-ray rocking curve topography (SXRCT), Nomarski optical microscopy (NOM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) are adopted to investigate the nature of the area defects. Apart from XRT images, these domain features are visible in the NOM images (Figure 2). SXRCT results show that these areas have a different strain level from the rest of the wafer area. SEM images in RBSD mode show that the area defects are observed as a diffraction contrast. To investigate the atomic configuration of these domains, HRTEM of specimens sliced from the domains are being compared with those from outside the domains. The characterization results from SXRCT, SEM and TEM analysis in conjunction with observations from other techniques like XRT and NOM will be discussed to determine the nature of the area defects and their formation mechanisms will be deduced.

[1] Y. Liu, B. Raghothamachar, H. Peng, T. Ailihumaer, M. Dudley, R. Collazo, J. Tweedie, Z. Sitar, F.S. Shahedipour-Sandvik, K.A. Jones, Journal of Crystal Growth 551 (2020) 125903.

[2] Y. Liu, H. Peng, T. Ailihumaer, B. Raghothamachar, M. Dudley, Journal of Electronic Materials 50 (2021) 2981-2989.