Time-/Current-Dependent Surge Current Capability of Fully-Vertical GaN-on-GaN PiN Diode With Conductivity Modulation

Abstract

Bipolar-mode operation is essential for surge current ruggedness of diodes in high-power applications. Different from indirect-bandgap Si and SiC, it is unclear whether hole injection in the direct-bandgap GaN can yield effective conductivity modulation and consequently enhance surge current tolerance. In this article, we systematically investigate the evolvement of surge current capability in a fully-vertical GaN-on-GaN PiN diode with surge pulsewidth (t surge) varying from 5μ s to 10 ms and peak surge current (Ipeak) up to 17.8 kA/cm2. Thanks to the desirable conductivity modulation even in the direct-bandgap GaN, the vertical GaN-on-GaN PiN diode exhibits a low differential specific on-resistance of 0.45 mΩ · cm2 and a high surge energy density of 282 J/cm2 in a 10-ms surge current test. In conjunction with the microsecond-level dynamic I-V characterizations, the photon-enhanced and thermally-enhanced conductivity modulation in GaN has been identified and analyzed, which plays an important role in the tsurge -Ipeak-dependent surge current characteristics. The desirable photon-enhanced and thermally-enhanced conductivity modulation and superior surge current capability show the potential of vertical GaN bipolar devices in high-power electronic applications.