Current Density Analysis of Thin Film Effect in Contact Area on LED Wafer

In order to clarify the theory of contact resistance, there are many reports in these years. Mathematically the constriction current is derived from Laplace equation at one contact. And numerical approach for constriction current analysis was also preformed by Minowa and Sawada. Furthermore, as an experimental approach, Sawada et al. are successful in in-situ observation of current constriction inside the contact utilizing the behavior of the wafer for light emitting diodes that light is emitted in the position where the current flows. In this study, we attempted to give consideration to how the constriction resistance changes for the thin film wafer by comparing an experimental method, an analytical method, and theoretical values. As results, it was proved that when the film is as thick as 200μm, both experimental results and analytical results roughly matched with the theoretical values of the constriction resistance. However, when the film gets thinner to 50μm, the constriction resistance was larger than the theoretical values (R=ρ/2a). In addition, the values of contact resistance almost matched with the experimental values. These results determine that contact resistance in the thin film can be calculated using electric field analysis.