Epitaxial growth and characterization of GaN thin films on graphene/sapphire substrate by embedding a hybrid-AlN buffer layer

• Published in: Applied surface science Vol. 494; pp. 644 - 650
• Main Authors: Ke, Wen-Cheng, Liang, Zhong-Yi, Tesfay, Solomun Teklahymanot, Chiang, Chih-Yung, Yang, Cheng-Yi, Chang, Kuo-Jen, Lin, Jia-Ching
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2019
• Subjects: AlN; GaN; Graphene; Schottky contact; Threading dislocation; AlN; Schottky contact; Threading dislocation; Graphene; GaN
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.07.211

This study investigates that high-quality GaN thin films can be grown on a few-layer graphene (FLG)/sapphire substrate by embedding a hybrid AlN buffer layer (BL). The hybrid AlN BL is constructed by low-temperature AlN nucleation layer (LT-AlN NL) and high-temperature AlN BL grown respectively by sputtering and metal organic chemical vapor deposition (MOCVD). The high density of edge-type threading dislocation (TD) in the GaN sample without hybrid AlN BL provide current leakage paths, resulting in a symmetric and temperature-independent I-V characteristic curve for a Ni-based Schottky contact. The excellent adhesion and uniform coverage of LT-AlN NL on the FLG layer by sputtering can overcome the nucleation issue and prevent the thermal etching effect of graphene during MOCVD epitaxial process. The edge-type TD density and carbon concentration of the GaN thin films grown on the hybrid AlN BL/FLG/sapphire substrate can be reduced significantly, resulting in a lower intensity of blue, green, and orange luminescences on a 17-K photoluminescence spectrum. The Ni-based Schottky contact with a barrier height of 0.69 eV and leakage current density of 4.38 × 10−6 A/cm2 is obtained, which demonstrates that a high-quality GaN thin films can be grown onto an FLG substrate by embedding a hybrid AlN BL. [Display omitted] •Graphene dissociation is suppressed by embedding a hybrid AlN buffer layer.•High crystalline quality of GaN thin-films is grown on a graphene substrate.•A PTC characteristic of Ni/GaN Schottky diode is obtained on a graphene substrate.