Electrical and structural properties of Ir/Ru Schottky rectifiers on n-type InGaN at different annealing temperatures

Abstract

The effect of annealing temperature on interface properties of iridium/ruthenium (Ir/Ru) Schottky contacts on n-type InGaN have been investigated by current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) techniques. An as-deposited Ru/Ir/n-InGaN Schottky diode exhibits a barrier height of 0.61eV (I–V) and 0.79eV (C–V), which increases to 0.71eV (I–V) and 0.96eV (C–V) after annealing at 200°C. A maximum barrier height of 0.73eV (I–V) and 1.02eV (C–V) is achieved for the Ir/Ru Schottky contacts after annealing at 300°C. Further, it is observed that the Schottky barrier height slightly decreases upon annealing at temperatures of 400°C and 500°C and the obtained values are 0.68eV (I–V), 0.93eV (C–V) and 0.66eV (I–V), 0.86eV (C–V), respectively. The Norde and Cheung’s methods are used to extract the barrier height (Φb), ideality factor (n) and series resistance (Rs). The interface state density is also determined by Terman’s method. According to the above results, the optimum annealing temperature for Ru/Ir/n-InGaN Schottky diode is 300°C. Based on the AES and XRD analysis, the formation of gallide phases at the Ru/Ir/n-InGaN interface could be the reason for the increase of Schottky barrier heights upon annealing temperatures. It is noted that overall surface morphology of Ir/Ru Schottky contacts is reasonably smooth even after annealing at 500°C as observed from AFM results.