Q: I am not sure whether practically LLO can be done on the PSS given it is not a flat surface

A: “laser lift-off” actually is according to “NL layer” as below image. If the NL layer is GaN layer, when it is heating to constant high temperature, the GaN is decomposed into Ga and nitrogen, and  nitrogen is released out, naturally the sapphire is seperated from epitaxial layer.So the main point is if the NL layer is GaN layer or not (some manufacturers use NL layer by AlN material, if so, it can not be laser lift off.)And we confirm our NL layer is GaN material.