Comparison of Surface Passivation Layers on InGaN/GaN MQW LEDs

The effect of different surface passivation films on blue or green (465-505 nm) InGaN/GaN multiquantum well light-emitting diodes (LEDs) die were examined. SiO₂or SiNx deposited by plasma enhanced chemical vapor deposition, or Sc₂O₃or MgO deposited by rf plasma enhanced molecular beam epitaxy all show excellent passivation qualities. The forward currentvoltage (I-V) characteristics were all independent of the passivation film used, even though the MBE-deposited films have lower interface state densities (3-5×10¹¹ eV-¹ cm-²) compared to the PECVD films (~10¹² eV-1 cm-²). The reverse I-V characteristics showed more variation, but there was no systematic difference for any of the passivation films. The results suggest that simple PECVD processes are effective for providing robust surface protection for InGaN/GaN LEDs.