Anisotropies of Structure, Optical Properties, Contact, and Epitaxy on (101)- and (001)-Oriented β-Ga<sub>2</sub>O<sub>3</sub> Crystal Planes
Bo Fu, Zhihong Yu, Haiting Wang, Qianwen Wang, Shujing Gao, Yingjie Qu, Xuzhao Zhang, Yujun Shi
Abstract
In this work, we studied the anisotropies of structure, optical properties, contact characteristics, and epitaxy on (101) and (001) β-Ga 2 O 3 substrates. The high-quality (101)- and (001)-oriented substrates with full width at half-maximum of less than 90 arcsec in the X-ray rocking curve were grown by the edge-defined film-fed growth method. The atomic arrangement of the (001) plane was terminated by Ga–O or O. The (101) plane was terminated by either Ga or O, resulting in 1–2 times higher-density surface dangling bonds than those of the (001) plane. The (101) substrate showed a higher period of angle-dependent Raman spectral intensities in plane, lower surface barrier height (Φ surf ) value, better Ohmic contact, and more desired rectification ratio by optical and electrical measurements. The lattice mismatch of ⟨0002⟩ GaN//⟨101⟩ β-Ga 2 O 3 and ⟨10–10⟩ GaN//⟨001⟩ β-Ga 2 O 3 was the same, while the orientations of GaN epitaxial films were completely different. Based on the comprehensive comparison, the anisotropies in the structure, optical properties, contact characteristics, and epitaxy between (101) and (001) substrates, even though from the same β-Ga 2 O 3 bulk crystal, are obvious. The (101) plane with higher-density surface dangling bonds not only exhibits an excellent Ohmic contact but also balances the Schottky contact. Furthermore, the (101) β-Ga 2 O 3 substrate is a good candidate for the heteroepitaxy of the (0002) GaN polar film.