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  • Enhancement Mode β-(Al x Ga 1-x ) 2 O 3 /Ga 2 O 3 Heterostructure FET (HFET) With High Transconductance and Cutoff Frequency
Title: Enhancement Mode β-(Al x Ga 1-x ) 2 O 3 /Ga 2 O 3 Heterostructure FET (HFET) With High Transconductance and Cutoff Frequency
Award ID(s):
2019749
PAR ID:
10343784
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
IEEE Electron Device Letters
Volume:
42
Issue:
10
ISSN:
0741-3106
Page Range / eLocation ID:
1444 to 1447
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. ; ; ; ; ; (, Applied Physics Letters)
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  2. ; ; ; ; ; ; ; ; (, ECS Journal of Solid State Science and Technology)
    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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  3. ; ; ; ; ; ; ; (, APL Materials)
    Phase pure β-(Al x Ga 1−x ) 2 O 3 thin films are grown on (001) oriented β-Ga 2 O 3 substrates via metalorganic chemical vapor deposition. By systematically tuning the precursor molar flow rates, the epitaxial growth of coherently strained β-(Al x Ga 1−x ) 2 O 3 films is demonstrated with up to 25% Al compositions as evaluated by high resolution x-ray diffraction. The asymmetrical reciprocal space mapping confirms the growth of coherent β-(Al x Ga 1−x ) 2 O 3 films (x < 25%) on (001) β-Ga 2 O 3 substrates. However, the alloy inhomogeneity with local segregation of Al along the ([Formula: see text]) plane is observed from atomic resolution STEM imaging, resulting in wavy and inhomogeneous interfaces in the β-(Al x Ga 1−x ) 2 O 3 /β-Ga 2 O 3 superlattice structure. Room temperature Raman spectra of β-(Al x Ga 1−x ) 2 O 3 films show similar characteristics peaks as the (001) β-Ga 2 O 3 substrate without obvious Raman shifts for films with different Al compositions. Atom probe tomography was used to investigate the atomic level structural chemistry with increasing Al content in the β-(Al x Ga 1−x ) 2 O 3 films. A monotonous increase in chemical heterogeneity is observed from the in-plane Al/Ga distributions, which was further confirmed via statistical frequency distribution analysis. Although the films exhibit alloy fluctuations, n-type doping demonstrates good electrical properties for films with various Al compositions. The determined valence and conduction band offsets at β-(Al x Ga 1−x ) 2 O 3 /β-Ga 2 O 3 heterojunctions using x-ray photoelectron spectroscopy reveal the formation of type-II (staggered) band alignment. 
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  4. ; ; ; ; ; (, Crystal Growth & Design)
  5. ; ; ; ; ; (, Journal of Vacuum Science & Technology A)
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