Investigation of conductivity modulation in vertical GaN-on-GaN PiN diode under high current density
Yanjun Li, Shu Yang, Fengwei Ji, Xi Tang, Kuang Sheng
Abstract
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 ∼0.1 kA/cm2 to 620 K at ∼9.0 kA/cm2 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 ∼200 J/cm2 in the GaN PND, showing the potential of vertical GaN-on-GaN power devices in the high electro-thermal-ruggedness application.