Epitaxial growth of β-Ga 2 O 3 (−201) thin film on four-fold symmetry CeO 2 (001) substrate for heterogeneous integrations

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2021-11, Vol.9 (44), p.15868-15876
• Main Authors: Tang, Xiao, Li, Kuang-Hui, Liao, Che-Hao, Zheng, Dongxing, Liu, Chen, Lin, Rongyu, Xiao, Na, Krishna, Shibin, Tauboada, Jose, Li, Xiaohang
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D1TC02852A

β-Ga 2 O 3 is a wide bandgap semiconductor material that is promising for many fields such as gas sensors, UV detectors, and high-power electronics. Until now, most epitaxial β-Ga 2 O 3 thin films could only be realized on six-fold symmetric single crystal substrates including sapphire (0001), 3C-SiC (001), and native β-Ga 2 O 3 . In this report, we demonstrate the epitaxial growth of β-Ga 2 O 3 (−201) thin films on non-six-fold symmetric substrates, i.e. , the CeO 2 (001) substrate. Different from the conventional six-fold symmetric sapphire substrates, the four-fold symmetric cubic phase CeO 2 (001) induces the formation of two sets of hexagonal-like atom frameworks with a mutual rotation angle of 90° in the β-Ga 2 O 3 (−201) plane. This is due to the small lattice mismatch between the β-Ga 2 O 3 (−201) plane and the CeO 2 (001) plane in two directions: CeO 2 [100]//β-Ga 2 O 3 [010] and CeO 2 [010]//β-Ga 2 O 3 [010]. Besides, the valence band offset (VBO) and the conduction band offset (CBO) at the β-Ga 2 O 3 /CeO 2 heterojunction are examined using high-resolution X-ray photoelectron spectroscopy (HR-XPS) and are estimated to be 1.63 eV and 0.18 eV, respectively, suggesting a type-II heterostructure. The obtained epitaxial β-Ga 2 O 3 thin films are fabricated into photodetectors (PDs), which show key photoelectrical characteristics that are similar to those of PDs using the conventional sapphire substrate. The results indicate the epitaxial β-Ga 2 O 3 thin films on CeO 2 have a high crystallization quality, and thus are capable of producing various essential devices. Moreover, the epitaxy between β-Ga 2 O 3 (−201) and CeO 2 (001) demonstrated in this work can pave the way for constructing heterostructures between β-Ga 2 O 3 and other cubic-phase functional materials, such as p-type semiconductors, piezoelectric semiconductors, and superconductors.