Effects of thermal annealing on the electrical and structural properties of Mo/Au schottky contacts on n-GaN

摘要

The current conduction mechanisms of the Mo/Au Schottky contacts on n-GaN with post metal annealing at 300, 500 and 700 degrees C have been investigated. The barrier height phi(B) and ideality factor n directly extracted from the measured current-voltage characteristics based on the thermionic emission (TE) theory show variations with the temperature, suggesting that inhomogeneous barrier heights were formed. A modified TE model considering the barrier height inhomogeneity with a Gaussian distribution was found to be able to explain the measurement data well. From the modified Richardson plot, the mean barrier heights (phi(B)) over bar = 0.598, 0.566, 0.789, 0.567 eV and the standard deviations sigma(0) = 125.70, 113.14, 89.77, 121.24 meV were obtained for the sample with as-deposited Mo/Au, the one with post metal annealing at 300 degrees C, the one annealed 500 degrees C and the one annealed at 700 degrees C, respectively. The specific on-resistance doesnot show any obvious change after post thermal annealing. The best values of reverse leakage current and the breakdown voltage were achieved after post metal annealing at 500 degrees C. Transmission Electron Microscopy (TEM) images and energy dispersive X-ray (EDX) spectroscopy mapping results reveal that the interaction between Mo and GaN during the annealing contributes to the observed Schottky barrier height difference under different annealing conditions. (c) 2020 Elsevier B.V. All rights reserved.