I-V and C-V characteristics of rare-earth-metal/p-GaN Schottky contacts

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The electrical properties of rare-earth-metal Schottky contacts top-GaN were characterized with current-voltage (I-V) and capacitance-voltage (C-V) measurements for the first time. Threekinds of rare-earth-metal films of Dy, Er, and Gd, which havelow-metal-work-function nature, were deposited on low-Mgdopedp-GaN. Linear regions of more than one and a half orderswere seen in a forward semi-log I-V plot, and reverse breakdown voltages were as high as around 60 V for all samples. Inthe C-V characteristics, good linearity was obtained in a 1/C^2 plotfor all samples. The carrier concentration was estimated to beabout 5.5×10^16 cm^<-3>, which is a reasonable value of activation efficiencyof 4.2%. The Schottky barrier heights of Dy, Er, and Gdcontacts were 1.91, 2.38, and 2.16 eV from I-V, and 1.79, 1.78,and 1.70 eV from C-V, respectively. These values are as high asthose of the transition metal contacts. These results tell us thatFermi level pinning is significantly strong for p-GaN surfaceswith a conventional acid treatment.