4.6 Article

Band alignment and band bending at α-Ga2O3/ZnO n-n isotype hetero-interface

Journal

APPLIED PHYSICS LETTERS
Volume 115, Issue 20, Pages -

Publisher

AMER INST PHYSICS
DOI: 10.1063/1.5126325

Keywords

-

Funding

  1. National Key RD Program [2018YFB0406502]
  2. State Key RAMP
  3. D project of Jiangsu [BE2018115]
  4. National Nature Science Foundation [61774081, 91850112]
  5. Natural Science Foundation of Jiangsu Province [BK20161401]
  6. Shenzhen Fundamental Research Project [201773239, 201888588, 20180307163240991]
  7. State Key Laboratory of Wide-Bandgap Semiconductor Power Electric Devices [2017KF001]
  8. Fundamental Research Funds for the Central Universities [021014380135, 021014380112, 021014380110]

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Understanding the electronic structures at the interfaces of wide bandgap oxide heterostructures is crucial for the rational design of oxide-based optoelectronic devices with novel functionality and improved performance. In this work, the electronic band diagram at a ZnO/alpha-Ga2O3 n-n isotype heterojunction is investigated by depth-profile x-ray photoemission spectroscopy (XPS). The directly measured valence-band offset is -0.61 +/- 0.1 eV and a type-I (straddling gap) band alignment is formed at the ZnO/alpha-Ga2O3 heterointerface. As probed by the depth profile of core-levels and VB-XPS, the formation of an interfacial layer is observed due to Ga and Zn interdiffusion, where charged interfacial states result in the downward and upward band-bending at the ZnO and alpha-Ga2O3 sides, respectively. The influence of band bending and band discontinuity at the interface is confirmed by the rectifying characteristics in the Au/alpha-Ga2O3/ZnO heterojunction with electron accumulation at its interface. Taking the thermionic-field emission and band-to-band tunneling mechanisms into account, the simulated transport properties agrees well with the reported I-V characteristics of Au/alpha-Ga2O3/ZnO avalanche photodiode, a further validation of the deduced band alignment of the heterostructure. Published under license by AIP Publishing.

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