High Voltage Vertical GaN p-n Diodes With Hydrogen-Plasma Based Guard Rings

This letter demonstrates novel hydrogen-plasma based guard rings (GRs) for high voltage vertical GaN p-n diodes grown on bulk GaN substrates by metalorganic chemical vapor deposition (MOCVD). The GR structure can significantly improve breakdown voltages (BV) and critical electric fields (Ec) of the devices. Not having field plates or passivation, the p-n diodes with a 9 μm drift layer and 10 GRs showed BV/on-resistance (Ron) of 1.70 kV/0.65 mΩ·cm2, which are close to the GaN theoretical limit. Moreover, the device also exhibited good rectifying behaviors with an on-current of ~ 2.6 kA/cm2, an on/off ratio of ~ 1010, and a turn-on voltage of 3.56 V. This work represents one of the first effective GR techniques for high performance kV-class GaN p-n diodes.