The influence of carbon in the back-barrier layers on the surface electric field peaks in GaN Schottky diodes

Technology Computer Aided Design simulations are used to assess the influence of carbon in the back-barrier layers of GaN-on-Si wafers on the voltage distribution in GaN Schottky diodes. It is shown that carbon cannot be present as an acceptor only - as it is commonly assumed. The carbon needs to be compensated by donors or partly electrically inactive in order to explain the observed high hard breakdown voltage in GaN-on-Si Schottky diodes. Furthermore, it is shown that the level of donor compensation of the carbon will have a significant influence on the two-dimensional voltage distribution in the devices, and, hence, on the surface electric field peaks. This conclusion is important to consider in the design of field plate extensions of the Schottky diode.