Investigation of conductivity modulation in vertical GaN-on-GaN PiN diode under high current density

This work studies the conductivity modulation in the vertical GaN-on-GaN PiN diode (PND) under high current density and its impact on surge current capability. Thanks to the direct-bandgap of GaN, the junction temperature at different current densities could be characterized by both photo-luminescence and electro-luminescence measurements. The junction temperature rises from 300 K at similar to 0.1 kA/cm(2) to 620 K at similar to 9.0 kA/cm(2) with emission peaks shifted from 3.38 to 3.21 eV. Meanwhile, the electro-thermal behavior of the vertical GaN PND shows that the hole concentration in p-GaN is increased due to self-heating, leading to enhanced conductivity modulation and negative temperature-dependence of ON-resistance, which is desirable for surge current capability. The heat accumulation in GaN under surge current condition could be suppressed by the enhanced conductivity modulation. The surge energy density can reach similar to 200 J/cm(2) in the GaN PND, showing the potential of vertical GaN-on-GaN power devices in the high electro-thermal-ruggedness application.