Journal
MATERIALS RESEARCH BULLETIN
Volume 144, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.materresbull.2021.111478
Keywords
MgO; ZnO; Schottky-barrier diodes; Schottky-barrier height; Oxygen vacancies
Categories
Funding
- Ministry of Science and Technology of the Republic of China, Taiwan
- MOST [109-2112-M-415-002]
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The study showed that inserting a thin MgO layer between Au and annealed-ZnO in Schottky-barrier diodes can significantly reduce leakage current and enhance rectification ratio, leading to an increased Schottky-barrier height.
The effects of a thin MgO insertion layer between Au and annealed-ZnO on the Schottky-barrier diodes (SBDs) of Au/annealed-ZnO were studied. The structure of Au/as-deposited ZnO (SBD_A) presents a rather leaky (near ohmic) characteristic owing to the presence of oxygen vacancies on the ZnO surface. After post-annealing of ZnO in air, the Au/annealed-ZnO (SBD_B) exhibits a rectifying behavior as a result of the compensated oxygen vacancies. Upon inserting a MgO film between the Au and annealed-ZnO, the leakage current is significantly reduced by approximately 3-orders of magnitude in the Au/MgO/annealed-ZnO structure (SBD_C), largely enhancing the rectification ratio from 10.3 to 731. This is because the oxygen vacancies are further reduced by the MgO modification of ZnO. The post-ZnO annealing and MgO insertion increased the Schottky-barrier height (SBH) from 0.58 to 0.68 and 1.1 eV in SBD_A, SBD_B, and SBD_C, respectively. Hence, the MgO insertion not only decreases the oxygen vacancies on the ZnO surface, it also increases the SBH. X-ray diffraction, X-ray photoelectron spectroscopy, and band-diagrams were employed to elucidate the mechanisms of the increase in SBH.
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