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In this work, the structural and electrical properties of metalorganic chemical vapor deposited Si-doped β-(Al x Ga 1−x ) 2 O 3 thin films grown on (010) β-Ga 2 O 3 substrates are investigated as a function of Al composition. The room temperature Hall mobility of 101 cm 2 /V s and low temperature peak mobility (T = 65 K) of 1157 cm 2 /V s at carrier concentrations of 6.56 × 10 17 and 2.30 × 10 17 cm −3 are measured from 6% Al composition samples, respectively. The quantitative secondary ion mass spectroscopy (SIMS) characterization reveals a strong dependence of Si and other unintentional impurities, such as C, H, and Cl concentrations in β-(Al x Ga 1−x ) 2 O 3 thin films, with different Al compositions. Higher Al compositions in β-(Al x Ga 1−x ) 2 O 3 result in lower net carrier concentrations due to the reduction of Si incorporation efficiency and the increase of C and H impurity levels that act as compensating acceptors in β-(Al x Ga 1−x ) 2 O 3 films. Lowering the growth chamber pressure reduces Si concentrations in β-(Al x Ga 1−x ) 2 O 3 films due to the increase of Al compositions as evidenced by comprehensive SIMS and Hall characterizations. Due to the increase of lattice mismatch between the epifilm and substrate, higher Al compositions lead to cracking in β-(Al x Ga 1−x ) 2 O 3 films grown on β-Ga 2 O 3 substrates. The (100) cleavage plane is identified as a major cracking plane limiting the growth of high-quality Si-doped (010) β-(Al x Ga 1−x ) 2 O 3 films beyond the critical thicknesses, which leads to highly anisotropic and inhomogeneous behaviors in terms of conductivity.
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Probing Charge Transport and Background Doping in Metal‐Organic Chemical Vapor Deposition‐Grown (010) β‐Ga 2 O 3
A new record‐high room‐temperature electron Hall mobility (μRT = 194 cm2 V−1 s−1atn ≈ 8 × 1015 cm−3) for β‐Ga2O3is demonstrated in the unintentionally doped thin film grown on (010) semi‐insulating substrate via metal‐organic chemical vapor deposition (MOCVD). A peak electron mobility of ≈9500 cm2 V−1 s−1is achieved at 45 K. Further investigation on the transport properties indicates the existence of sheet charges near the epilayer/substrate interface. Si is identified as the primary contributor to the background carrier in both the epilayer and the interface, originating from both surface contamination and growth environment. The pregrowth hydrofluoric acid cleaning of the substrate leads to an obvious decrease in Si impurity both at the interface and in the epilayer. In addition, the effect of the MOCVD growth condition, particularly the chamber pressure, on the Si impurity incorporation is studied. A positive correlation between the background charge concentration and the MOCVD growth pressure is confirmed. It is noteworthy that in a β‐Ga2O3film with very low bulk charge concentration, even a reduced sheet charge density plays an important role in the charge transport properties.
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- Award ID(s):
- 1810041
- PAR ID:
- 10159699
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- physica status solidi (RRL) – Rapid Research Letters
- Volume:
- 14
- Issue:
- 8
- ISSN:
- 1862-6254
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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