Over 1 GW/cm2 for high-power GaN p-i-n diodes with edge termination structure and laser annealing

In this article, the authors report the fabrication and characterization of quasi-vertical gallium nitride (GaN) p-i-n diodes grown on patterned sapphire substrates. In order to reduce diode leakage current and enhance breakdown voltage, the authors design the diodes having the structures of edge termination with a multi-mesa structure coupled with a field plate. Besides, the laser annealing is used to decrease the contact resistance and lower the forward voltage. Combining these processes, the fabricated p-i-n diodes with a 5 μm i-layer exhibit a specific on-resistance (RONA) of 0.47 mΩ cm2 and a breakdown voltage (VB) of 835 V. The corresponding Baliga’s figure of merit (VB2/RONA) is 1.48 GW/cm2, which is the highest ever reported for a GaN p-i-n diode grown on a sapphire substrate. Finally, depositing an aluminum layer onto the mesa surface can effectively block the ultraviolet emission out of the diode under forward bias.