Effects of UV/O3 and O2 plasma surface treatments on the band-bending of ultrathin ALD-Al2O3 coated Ga-polar GaN

Abstract
The recently demonstrated semiconductor grafting approach allows one to create an abrupt, low interface-trap-density heterojunction between a high-quality p-type single-crystalline semiconductor (non-nitrides) with n-type GaN. However, due to the surface band-bending from GaN polarization, an energy barrier exists at the grafted heterojunction, which can impact the vertical charge carrier transport. Reducing the energy barrier height is essential for some advanced device development. In this work, we employed UV/O3 and O2 plasma to treat a Ga-polar GaN surface with/without an ultrathin (∼2 nm) ALD-Al2O3 coating and studied the effects of the treatments on surface band-bending. Through XPS measurements, it was found that the treatments can suppress the upward band-bending of the Ga-polar GaN by 0.11–0.39 eV. The XPS results also showed that UV/O3 treatment is an effective surface cleaning method with little surface modification, while O2 plasma causes a strong oxidation process that occurs inside the top layer GaN.

Acknowledgements
The work was supported by the Air Force Office of Scientific Research under Grant No. FA9550-21-1-0081. This publication is partially based upon work supported by the King Abdullah University of Science and Technology (KAUST) under Award No. ORFS-CRG11-2022-5079.

Publisher
AIP Publishing

Journal
Journal of Applied Physics

DOI
10.1063/5.0188768

Additional Links
https://pubs.aip.org/jap/article/135/11/115303/3277854/Effects-of-UV-O3-and-O2-plasma-surface-treatments

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