Optica, Optical Materials Express, 8(12), p. 3273, 2022
DOI: 10.1364/ome.462192
Full text: Download
In this article, we determine the band alignment at the thermodynamically stable heterointerface between a ( 2 ¯ 01 )-oriented single-domain β-(In0.072Ga0.928)2O3 crystal and bulk c-plane sapphire, namely, (0001)-oriented α-Al2O3. The β-(In0.072Ga0.928)2O3 layer was deposited on the bulk sapphire crystal using pulsed laser deposition. The β-(In0.072Ga0.928)2O3 and α-Al2O3 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-Al2O3/β-(In0.072Ga0.928)2O3 heterojunction. X-ray diffraction measurements confirmed ( 2 ¯ 01 )-oriented single-domain β-(In0.072Ga0.928)2O3 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 2p and Ga 2p3/2 with respect to the valence band maxima of the β-(In0.072Ga0.928)2O3 and α-Al2O3 layers, respectively. Then, we measured the energy separation between the Al 2p and Ga 2p3/2 core levels at the interface of the heterojunction. β-(InGa)2O3 is a wide-bandgap semiconductor, while α-Al2O3 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.