Q:For 4” pss wafer, the light comes out from the p-GaN side not from sapphire, so I can’t do flip chip packaging. Also I don’t know whether laser liftoff is possible for pss wafer.
Is it possible you can share any image of the etched surface of pss?
A: 4″LED wafer on pps also can be LLO(NL-buffer layer is GaN). Again,LED light is sourcing from mqw light, emitting in all directions, p-GaN is positive(front side), it will naturally light,also each backside will light.At the bottom of the sapphire is also light, and then through the reflected light from other angles