Self-Separation of GaN Using In-Situ Deposited SiN as Separation Layer

Thick, self-separated GaN layers have been grown by hydride vapor phase epitaxy (HVPE) on templates with SiN-interlayers, which worked as the separation layer. The used templates were prepared by metalorganic vapor phase epitaxy (MOVPE) to start with an excellent seed layer. As several groups reported, it was observed, that by using only one SiN-interlayer, the dislocation density could be reduced by an order of magnitude. To use the SiN-interlayer as separation layer, a much weaker connection between the template and the thick HVPE grown GaN should be generated. To study the separation process in-depth, we started our studies with a stack of multiple SiN-interlayers. Those structures lead to large masked areas or even, by the right choice of the deposition parameters, to a cavernous layer. On those templates, the separation during the cool down of nearly full 2 inch wafers could be observed. These thick self-separated HVPE layers showed a smooth surface morphology with excellent optical and electrical properties.