X Ray Photoelectron Spectroscopy was used to measure valence band offsets for Al 2 O 3 deposited by Atomic Layer Deposition on α -(Al x Ga 1-x ) 2 O 3 alloys over a wide range of Al contents, x, from 0.26–0.74, corresponding to a bandgap range from 5.8–7 eV. These alloys were grown by Pulsed Laser Deposition. The band alignments were type I (nested) at x <0.5, with valence band offsets 0.13 eV for x = 0.26 and x = 0.46. At higher Al contents, the band alignment was a staggered alignment, with valence band offsets of − 0.07 eV for x = 0.58 and −0.17 for x = 0.74, ie. negative valence band offsets in both cases. The conduction band offsets are also small at these high Al contents, being only 0.07 eV at x = 0.74. The wide bandgap of the α -(Al x Ga 1-x ) 2 O 3 alloys makes it difficult to find dielectrics with nested band alignments over the entire composition range.
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In situ MOCVD growth and band offsets of Al 2 O 3 dielectric on β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 thin films
The in situ metalorganic chemical vapor deposition (MOCVD) growth of Al 2 O 3 dielectrics on β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 films is investigated as a function of crystal orientations and Al compositions of β-(Al x Ga 1−x ) 2 O 3 films. The interface and film qualities of Al 2 O 3 dielectrics are evaluated by high-resolution x-ray diffraction and scanning transmission electron microscopy imaging, which indicate the growth of high-quality amorphous Al 2 O 3 dielectrics with abrupt interfaces on (010), (100), and [Formula: see text] oriented β-(Al x Ga 1−x ) 2 O 3 films. The surface stoichiometries of Al 2 O 3 deposited on all orientations of β-(Al x Ga 1−x ) 2 O 3 are found to be well maintained with a bandgap energy of 6.91 eV as evaluated by high-resolution x-ray photoelectron spectroscopy, which is consistent with the atomic layer deposited (ALD) Al 2 O 3 dielectrics. The evolution of band offsets at both in situ MOCVD and ex situ ALD deposited Al 2 O 3 /β-(Al x Ga 1−x ) 2 O 3 is determined as a function of Al composition, indicating the influence of the more »
- Publication Date:
- NSF-PAR ID:
- 10383185
- Journal Name:
- Journal of Applied Physics
- Volume:
- 132
- Issue:
- 16
- Page Range or eLocation-ID:
- 165301
- ISSN:
- 0021-8979
- Sponsoring Org:
- National Science Foundation
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