Graphene-GaN Schottky diodes
graphene, GaN, Schottky diode, Schottky barrier height, Fermi level pinning
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.
Tsinghua University Press
Seongjun Kim,Tae Hoon Seo,Myung Jong Kim,Keun Man Song,Eun-Kyung Suh,Hyunsoo Kim, Graphene-GaN Schottky diodes. NanoRes.2015, 8(4): 1327–1338