Electrical and Optical Characterization of Ni/Al0.3Ga0.7N/GaN Schottky Barrier Diodes

Ni/AlGaN/GaN Schottky barrier diodes were characterized by electrical and optical measurements. Analysis of temperature-dependent (80 K to 550 K) current–voltage characteristics considering various transport mechanisms shows that the tunneling current dominates in the samples investigated. Thermionic emission current, extracted from the total current by a fitting procedure, yielded an effective barrier height of 1.36 eV to 1.39 eV at 300 K, and its slight decrease with increased temperature. This result shows that significantly lower barrier heights reported before (0.73 eV to 0.96 eV) follow from an assumption that the measured and thermionic currents are equal. The barrier height of 1.66 eV extracted from photoemission measurements confirms that electrically evaluated barrier heights are underestimated. The tunneling current contribution is considered to be dislocation governed, and a dislocation density of about 2 × 10 8 cm −2 is calculated.