Improving electrical properties of metal–semiconductor contact on Al-rich n-AlGaN by multi-step annealing

作者：Xiang Guo, Jing Lang, Fujun Xu, Jiaming Wang, L. S. Zhang, Zhiyong Zhang, Ji Chen, F. Y. Tan, Chengzhi Ji, Xiangning Kang, Xuelin Yang, Ning Tang, Xinqiang Wang, Weikun Ge, Bo Shen · 发表于：Applied Physics Letters · 年份：2025 · DOI：10.1063/5.0285985 · 被引用次数：2 · 研究领域：GaN-based semiconductor devices and materials、Photocathodes and Microchannel Plates、Semiconductor materials and devices

N-type Ohmic contact on Al-rich AlGaN has garnered special attention, thanks to its crucial impact on the performance of deep ultraviolet devices, which are experiencing a surge in demand. However, the Ohmic contact is still suffering from the poor matching of energy band at metal–semiconductor interface. In this work, multi-step annealing is proposed to facilitate the Ohmic contact between Ti/Al/Ni/Au electrodes and n-AlGaN with Al composition higher than 60%. It is found that the first low-temperature annealing is capable to effectively suppress the excessive diffusion of Ti metal, which enables the generation of low-work function TiN film on the n-AlGaN, while the subsequent high-temperature annealing is adopted to provide an adequate driving force for breaking the N-related bonds with high bond energy, which gives rise to a large number of N-vacancies on the surface of n-AlGaN and, consequently, contributes to a high electron concentration. Thanks to the aforementioned two processes, the electron tunneling barrier height and width can be reduced, thus promoting the formation of Ohmic contact on etched n-Al0.65Ga0.35N, with a specific contact resistivity is as low as 2.58 × 10−4 Ω cm2.