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 ( ${E}_{c}$ ) of the devices. Not having field plates or passivation, the p-n diodes with a $9~\mu \text{m}$ drift layer and 10 GRs showed BV /on-resistance ( ${R}_{\textit {on}}$ ) of 1.70 kV/0.65 $\text{m}\Omega \cdot $ 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.