Optimizing Structured SiN-masks for Self Separation of Full 2”-GaN Wafers by Hydride Vapor Phase Epitaxy

Using a previously shown method, we prepared 2”-GaN wafers as templates for a self separation process. Self separation is happening during cooldown after growing thick layers of GaN in our hydride vapor phase epitaxy (HVPE) reactor. Our templates consist of GaN grown by metalorganic vapor phase epitaxy (MOVPE) directly on sapphire. These GaN layers are masked with 200nm of SiN that are structured by means of optical lithography. They are subsequently overgrown with a thin GaN layer by metalorganic vapor phase epitaxy (MOVPE). Previous experiments found that the ideal interlayer for self separation during cooldown in HVPE is created when using a hexagonally shaped pattern as mask. We now tried several possible variations of this pattern to find the optimal geometrical proportions supporting the desired self separation.