The influence of undoped GaN surface flatness on the properties of the blue light-emitting diode wafer
We have studied the properties of blue-LED wafers grown on GaN with similar dislocation density and different surface flatness. Results indicate that the smooth surface morphology of the undoped GaN layer leads to better layer periodicity in multiple quantum well (MQW) and smooth surface morphology of LED wafers. The surface flatness of the undoped GaN layer has little effect on the forward voltage and output power of the LED. However, the reverse leakage current and the lifetime of the LED wafer grown on the flatter GaN layer improved evidently. On the other hand, wafers grown on the GaN layer with worse surface flatness show better electrostatic discharge (ESD) characteristics.