Analysis on electrical characteristics of high-voltage GaN-based light-emitting diodes

In order to investigate their electrical characteristics, high-voltage light-emitting-diodes (HV-LEDs) each containing four cells in series are fabricated. The electrical parameters including varying voltage and parasitic effect are studied. It is shown that the ideality factors (IFs) of the HV-LEDs with different numbers of cells are 1.6, 3.4, 4.7, and 6.4. IF increases linearly with the number of cells increasing. Moreover, the performance of the HV-LED with failure cells is examined. The analysis indicates that the failure cell has a parallel resistance which induces the leakage of the failure cell. The series resistance of failure cell is 76.8 Ω, while that of normal cell is 21.3 Ω. The scanning electron microscope (SEM) image indicates that different metal layers do not contact well. It is hard to deposit the metal layers in the deep isolation trenches. The fabrication process of HV-LED needs to be optimized.