Investigation of HVPE grown layers on MOVPE GaN/sapphire templates for application as drift layer in vertical GaN power devices

We report our investigations on HVPE grown GaN with thickness of $20 \mu m$ on MOVPE GaN/Sapphire templates. The important characteristics for the proposed electric functionalities as drift layer in vertical devices as GaN power MOSFETs are the surface morphology and the doping concentration of the HVPE grown layer, which are characterized by AFM and CV measurements on Schottky diodes, respectively. The surface topography is sufficiently flat for forming well-defined junctions in the following overgrowth. The unintentional doping concentration of the HVPE grown layer is approaching a suitable low level enabling the control of the intentional doping level for drift layers in power devices.