Temperature dependence of current-voltage characteristics of Ni-AlGaN/GaN Schottky diodes

Ni-AlGaN/GaN Schottky barrier diodes (SBDs) with lateral geometry were fabricated on sapphire substrates. At 300 K, devices with 500 - μ m -diameter Schottky contacts exhibited breakdown voltage ( V B ) of 765 V, forward current ( I F ) of 0.065 A at 1.5 V, and specific on-resistance ( R on ) of 81.3 m Ω cm 2 , producing a figure-of-merit ( V B 2 / R on ) of ∼ 7.2 MW cm − 2 . Measured in multifinger patterns, the same parameters were 420 V, 3.2 A, 4.6 m Ω cm 2 , and 38.4 MW cm − 2 , respectively, at 300 K. With the increase in measurement temperature from 300 to 450 K, SBDs with dimensions of 3000 × 3000 μ m 2 showed larger effective barrier heights (0.8 eV at 300 K and 1.27 eV at 475 K) and a slightly negative temperature coefficient ( − 0.48 V K − 1 ) for reverse breakdown voltage, while there was a little change in reverse leakage current. These results show the strong influence of barrier height inhomogeneity on the temperature dependence of apparent barrier heights obtained through current-voltage measurements.