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-mu 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 Omega cm(2), producing a figure-of-merit (V(B)(2)/R(on)) of similar to 7.2 MW cm(-2). Measured in multifinger patterns, the same parameters were 420 V, 3.2 A, 4.6 m Omega 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 x 3000 mu 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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525931]