Demonstration of AlGaN/GaN HEMTs on vicinal sapphire substrates with large misoriented angles
Haochen Zhang, Yue Sun, Kang‐Il Song, Chong Xing, Lei Yang, Danhao Wang, Huabin Yu, Xueqiang Xiang, Nan Gao, Guangwei Xu, Haiding Sun, Shibing Long
Abstract
In this work, the electrical characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) on vicinal c-plane sapphire substrates with different misoriented angles are investigated. As the angle increases from 0.2°, 1.0° to 4.0°, an enlarged width and height of surface step bunching as well as significantly enhanced electron mobility from 957, 1123 to 1246 cm2/V s were measured. As a result, a large boost in the maximum output current (IDmax) from ∼300 mA/mm (on a 0.2° substrate) to ∼650 mA/mm (on a 4.0° substrate) can be observed. Importantly, HEMTs on 1.0° and 4.0° substrates exhibit an obvious anisotropic electrical behavior: the IDmax along the [11-20] orientation is larger than that along the [10-10] orientation. Such a difference becomes more distinct as the misoriented angle increases, attributing to the lifted step height that would introduce a potential barrier for the electron transport along the [10-10] orientation. In short, this work demonstrates an effective approach toward the realization of high-performance HEMTs with anisotropic electrical behavior on a single device platform.