Graphene-GaN Schottky diodes
- Graphene-GaN Schottky diodes
- Seongjun Kim; Tae Hoon Seo; 김명종; Keun Man Song; Eun-Kyung Suh; Hyunsoo Kim
- Graphene; GaN; Schottky diodes
- Issue Date
- NANO RESEARCH
- VOL 8, NO 4, 1327-1338
- The electrical characteristics of graphene Schottky contacts formed on undoped GaN semiconductors were investigated. Excellent rectifying behavior with a rectification ratio of ∼107 at ±2 V and a low reverse leakage current of 1.0 × 10−8 A/cm2 at −5 V were observed. The Schottky barrier heights, as determined by the thermionic emission model, Richardson plots, and barrier inhomogeneity model, were 0.90, 0.72, and 1.24 ± 0.13 eV, respectively. Despite the predicted low barrier height of ∼0.4 eV at the graphene-GaN interface, the formation of excellent rectifying characteristics with much larger barrier heights is attributed to the presence of a large number of surface states (1.2 × 1013 states/cm2/eV) and the internal spontaneous polarization field of GaN, resulted in a significant upward surface band bending or a bare surface barrier height as high as of 2.9 eV. Using the S parameter of 0.48 (measured from the work function dependence of Schottky barrier height) and the mean barrier height of 1.24 eV, the work function of graphene in the Au/graphene/GaN stack could be approximately estimated to be as low as 3.5 eV. The obtained results indicate that graphene is a promising candidate for use as a Schottky rectifier in GaN semiconductors with n-type conductivity.
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