Growth and properties of metalorganic chemical vapor deposition-grown GaN templates using LT-GaN/AlN hybrid buffer layers

초록

This study presents a comparative analysis of the structural and optical properties of GaN epilayers grown on low-temperature GaN (LT-GaN), AlN, and LT-GaN/AlN hybrid buffer structures. All samples were deposited on cplane sapphire substrates. The AlN buffer layer was deposited by reactive RF magnetron sputtering, whereas the LT-GaN buffer layer and GaN epilayers were grown by metalorganic chemical vapor deposition (MOCVD). The surface morphology and surface energy were evaluated by atomic force microscopy (AFM) and contact angle measurements, respectively. The LT-GaN/AlN hybrid buffer exhibited the highest surface energy, leading to uniform nucleation and effective coalescence, which resulted in the formation of the smoothest GaN epilayer among the three samples. High-resolution X-ray diffraction (HR-XRD) rocking curve analysis revealed that the hybrid buffer sample showed the lowest full width at half maximum (FWHM) values for the (002) and (102) reflections, indicating a reduced dislocation density. Photoluminescence (PL) analysis confirmed near-band-edge (NBE) emission in all samples, while yellow luminescence (YL) was observed only in the LT-GaN single-buffer sample. These findings demonstrate that the LT-GaN/AlN hybrid buffer structure effectively enhances the crystalline and optical quality of GaN epilayers.

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