GaN is a promising material for more efficient high frequency and high voltage power switching. However, GaN still is not the common material for power electronics due to immature substrate, homoepitaxial growth, and processing technology. Electroluminescence is a promising method to predict failure points due to high field stress, which can assist in the separation of inherent defects stemming from substrate quality, and from process-induced defects as well as identify problems related to proper edge termination design. In this work, we compare the Electroluminescence signatures of devices on inhomogeneous substrates to DC I-V behavior to demonstrate the utility of the technique for process monitoring.