Effects of thin heavily Mg-doped GaN capping layer on ohmic contact formation of p-type GaN

• Published in: Semiconductor science and technology 2013-10, Vol.28 (10), p.105020
• Main Authors: Wu, L L, Zhao, D G, Jiang, D S, Chen, P, Le, L C, Li, L, Liu, Z S, Zhang, S M, Zhu, J J, Wang, H, Zhang, B S, Yang, H
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; contact; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in interface structures; Exact sciences and technology; heavily Mg-doped; P-GaN; Physics
• ISSN: 0268-1242; 1361-6641
• DOI: 10.1088/0268-1242/28/10/105020

The growth condition of thin heavily Mg-doped GaN capping layer and its effect on ohmic contact formation of p-type GaN were investigated. It is confirmed that the excessive Mg doping can effectively enhance the Ni Au contact to p-GaN after annealing at 550 °C. When the flow rate ratio between Mg and Ga gas sources is 6.4% and the layer width is 25 nm, the capping layer grown at 850 °C exhibits the best ohmic contact properties with respect to the specific contact resistivity (ρc). This temperature is much lower than the conventional growth temperature of Mg-doped GaN, suggesting that the deep-level-defect induced band may play an important role in the conduction of capping layer.