The junction temperature of n-ZnO nanorods/(p-4H-SiC, p-GaN, and p-Si) heterojunction light emitting diodes (LEDs) at built-in potential was modeled and experiments were performed at various temperatures (15-65 degrees C) to validate the model. As the LEDs operate near the built-in potential that's why it is interesting to investigate the temperature coefficient of forward voltage near the built-in potential (similar to V-o). The model and experimental values of the temperature coefficient of forward voltage near the built-in potential (similar to V-o) were compared. We measured the experimental temperature coefficient of the series resistance. By including the temperature coefficient of the series resistance in the model, the theoretical and experimental values become very close to each other. It was found that the series resistance has the main contribution in the junction temperature of our devices. We also measured the junction temperature above the built-in potential and found that the model deviates at higher forward voltage. From this observation we concluded that the model is applicable for low power devices, operated near the built-in potential. (C) 2010 Elsevier Ltd. All rights reserved.