Semi-polar (11–22) AlN epitaxial films on m-plane sapphire substrates with greatly improved crystalline quality obtained by high-temperature annealing

• Published in: Journal of crystal growth Vol. 570; p. 126207
• Main Authors: Xing, Kun, Cheng, Xueying, Wang, Liancheng, Chen, Shirong, Zhang, Yun, Liang, Huaguo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2021; Elsevier BV
• Subjects: Annealing; Atomic force microscopy; Compressive properties; Crystal structure; Crystallinity; Epitaxial growth; Grain size; High temperature; High temperature annealing; Low cost; Low defect density; Metalorganic chemical vapor deposition; Microscopy; MOCVD; Optoelectronic devices; Organic chemicals; Organic chemistry; Raman spectroscopy; Recrystallization; Sapphire; Semi-polar AlN growth; Stacking faults; Substrates; Semi-polar AlN growth; MOCVD; Low defect density; High temperature annealing
• DOI: 10.1016/j.jcrysgro.2021.126207
• ISSN: 0022-0248

•Semi-polar AlN film quality was massively improved by high-temperature annealing.•Neither a high-temperature MOCVD nor an ex situ sputtering process is required.•The proposed method provides better AlN quality than previously reported results.•The proposed method is suitable for mass-producing low-cost high-quality AlN film. This study addresses the difficulty of obtaining relatively low-cost semi-polar (11–22) AlN films epitaxially grown on m-plane sapphire substrates with high crystalline quality by applying a cost-effective high-temperature annealing process conducted at 1700 °C to films grown via standard-temperature metal organic chemical vapor deposition. The X-ray diffraction rocking curves of the annealed films along the [11–23] and [10–10] directions obtain full width at half maximum values of 0.152° and 0.193°, respectively. Atomic force microscopy results demonstrate the occurrence of a significant recrystallization process in the columnar formations of AlN films during annealing, resulting in increased AlN crystal grain size. Raman spectroscopy measurements reveal that the semi-polar (11–22) AlN films are subject to increased compressive stress after the annealing process. Transmission electron microscopy analyses confirm that our semi-polar AlN films provide appropriately low dislocation and basal stacking fault densities of 5.6 × 109 cm−2 and 1.05 × 105 cm−1, respectively. The proposed approach therefore obtains low-cost AlN films that are suitable for the mass manufacture of efficient optoelectronic devices.