The impact of threading dislocation density on Ni/n-GaN Schottky barrier diode characteristics was investigated using forward biased current-voltage-temperature (I-V-T) and internal photo-emission measurements. Nominally, identical metal-organic chemical phase deposition grown GaN layers were grown on two types of GaN templates on sapphire substrates to controllably varied threading dislocation density from 3 x 107 to 7 x 108/cm2. I-V-T measurements revealed thermionic emission to be the dominant transport mechanism with ideality factors near 1.01 at room temperature for both sample types. The Schottky barrier heights showed a similar invariance with threading dislocation density, with measured values of 1.12 to 1.13eV obtained from fitting the I-V-T results to a thermionic emission-diffusion model. The I-V-T results were verified by internal photo-emission measurements made on the same diodes, confirming that the Ni/n-GaN barrier heights do not showed a measurable threading dislocation density dependence for the threading dislocation density range measured here. In apparent contrast to this result was that the measured forward bias current-voltage characteristics indicated a shift in the observed forward bias turn-on voltage such that at the higher threading dislocation density value investigated here, a larger turn-on voltage (lower current) was observed. This difference was attributed to localized current blocking by high potential barrier regions surrounding threading dislocations that intersect the Ni/GaN interface. A simple model was presented that reconciles both the observed voltage shift and variations in the extracted Richardson constant as a function of threading dislocation density. With this model, an average local barrier surrounding dislocation of ~0.2V was obtained, which diverts current flow across the forward biased Schottky interface to non-dislocated regions.Effect of Threading Dislocation Density on Ni/n-GaN Schottky Diode I-V Characteristics. A.R.Arehart, B.Moran, J.S.Speck, U.K.Mishra, S.P.DenBaars, S.A.Ringel: Journal of Applied Physics, 2006, 100[2], 023709 (8pp)