Electrical properties of quasi-vertical Schottky diodes

In this paper, we report on quasi-vertical Schottky diodes on GaN on sapphire focusing on the influence of Ni/Au Schottky contact annealing and the doping concentration of the n-GaN onto their electrical properties. Schottky contact annealing is shown to improve the metal-semiconductor interface, as reflected in reduced ideality factor and increased barrier height. Additionally, a decrease of leakage currents and a drastic improvement of the breakdown field are achieved. The annealing temperature is shown to have an optimum value around 400 degrees C beyond which the device degrades. Further reduction of reverse leakage currents and an increase in breakdown voltage are achieved by decreasing the doping concentration in the n-GaN epitaxial layer. So far, a doping concentration of 2 x 10(16) cm(-3) showed the best results in terms of series resistance and breakdown behavior with R-on = 1 m Omega cm(2) and V-Br = 230 V.