Optical and interfacial characteristics of a heterojunction between (2¯01)-oriented single-domain β-(In 0.072 Ga 0.928 ) 2 O 3 and α-Al 2 O 3 crystals

• Published in: Optical materials express Vol. 12; no. 8; p. 3273
• Main Authors: Alfaraj, Nasir, Li, Kuang-Hui, Braic, Laurentiu, Hedhili, Mohamed Nejib, Guo, Zaibing, Ng, Tien Khee, Ooi, Boon S.
• Format: Journal Article
• Language: English
• Published: 01.08.2022
• ISSN: 2159-3930; 2159-3930
• DOI: 10.1364/OME.462192

In this article, we determine the band alignment at the thermodynamically stable heterointerface between a ( 2 ¯ 01 )-oriented single-domain β -(In 0.072 Ga 0.928 ) 2 O 3 crystal and bulk c -plane sapphire, namely, (0001)-oriented α -Al 2 O 3 . The β -(In 0.072 Ga 0.928 ) 2 O 3 layer was deposited on the bulk sapphire crystal using pulsed laser deposition. The β -(In 0.072 Ga 0.928 ) 2 O 3 and α -Al 2 O 3 valence and conduction band offsets (VBO and CBO, respectively) were found to be 0 ± 0.1 and 4.87 ± 0.1 eV, respectively. Accordingly, we identified a type-I α -Al 2 O 3 / β -(In 0.072 Ga 0.928 ) 2 O 3 heterojunction. X-ray diffraction measurements confirmed ( 2 ¯ 01 )-oriented single-domain β -(In 0.072 Ga 0.928 ) 2 O 3 high-quality films with in-plane rotations of every 120 ∘ , whereas Rutherford backscattering spectrometry was employed to verify the bulk composition. We employed high-resolution X-ray photoelectron spectroscopy to measure the core level binding energies of Al 2 p and Ga 2 p 3/2 with respect to the valence band maxima of the β -(In 0.072 Ga 0.928 ) 2 O 3 and α -Al 2 O 3 layers, respectively. Then, we measured the energy separation between the Al 2 p and Ga 2 p 3/2 core levels at the interface of the heterojunction. β -(InGa) 2 O 3 is a wide-bandgap semiconductor, while α -Al 2 O 3 is a well-known dielectric. Together, they can be employed to fabricate reliable and efficient power electronic devices. We also combined high-resolution transmission electron microscopy, X-ray diffraction, and fast Fourier transform algorithms to characterize the dislocations at the interface.