Diffusion-driven formation of current blocking layers in GaN using Mg-doped spin-on glass-based technique

This work reports the first demonstration of magnesium (Mg)-doped spin-on-glass based diffusion to achieve selective-area current-blocking layers in gallium nitride (GaN). We employed an oxygen-assisted annealing process to facilitate Mg diffusion into GaN. The optimized diffusion process enabled Mg concentration profiles exceeding 1 × 1019 cm−3 at depths beyond 200 nm. Diodes fabricated using this method exhibited enhanced blocking capabilities, increasing from under 30 V (in reference Schottky barrier diodes) to 200–400 V, depending on the annealing conditions. Devices annealed at 1050 °C demonstrated specific on-resistances of 7.3 mΩ cm2, comparable to the 3 mΩ cm2 observed in reference Schottky barrier diodes. In contrast, when the annealing was performed in N2 instead of an O2 ambient, Mg-diffused layers exhibited similar Mg concentrations and breakdown voltages to reference Schottky barrier diodes that did not go through the Mg diffusion process. These findings highlight the potential of oxygen-assisted two-step annealing as a viable technique for enabling Mg diffusion and forming effective current-blocking layers in GaN-based devices.