Electrical and structural properties of Au/Yb Schottky contact on p-type GaN as a function of the annealing temperature

The structural changes of Au/Yb contacts to p-type GaN were investigated using X-ray diffraction, X-ray photoemission spectroscopy, and atomic force microscopy as the annealing temperature was varied. The results were used to interpret the electrical properties of Au/Yb Schottky contacts to p-type GaN. A barrier height of 0.84 eV was obtained for the as-deposited Au/Yb/p-type GaN Schottky diode. An optimum barrier height of 1.03 eV was obtained for the 400 degrees C annealed Au/Yb/p-type GaN Schottky diode and the barrier height decreased after annealing at temperatures above 500 degrees C. Intermixing between the Au and Yb films occurred, implying an interfacial reaction between Au and Yb during deposition followed by a massive diffusion of Au towards GaN with increasing annealing temperature. The increase in the barrier height for the 400 degrees C annealed Au/Yb/p-type GaN contact could be associated with the formation of YbN phase, which creates nitrogen vacancies acting as donors in the vicinity of the metal/GaN interface region. The decrease in the barrier height after annealing at 500 and 600 degrees C could be due to the evolution of gallide phases, which generate Ga vacancies, leading to an increase in the net hole concentration near the metal/GaN interface. (C) 2016 Elsevier B.V. All rights reserved.