Vertical GaN diode offers superior surge current capability
Researchers from University of Science and Technology of China (USTC) have developed a 2 kV/0.45 mΩ·cm2 vertical GaN PiN diode with a high surge energy density (Esurge) of 282 J/cm2, which the team believes is one of the best among the state-of-the-art quasi- and fully-vertical GaN power diodes.
Power diodes are required to withstand high surge current resulting from ESD, current overshoot/oscillation or circuit failure. Minority carrier injection and conductivity modulation are essential for achieving high surge current in bipolar devices, which have been demonstrated for indirect-bandgap Si and SiC power devices with relatively long minority carrier lifetime. However, whether the conductivity modulation can occur and consequently enhance the surge current capability in the direct-bandgap GaN power devices with ultrashort intrinsic hole lifetime (~10-9 s) has been seldom reported to date.
The team investigated the evolution of the surge current capability in vertical GaN PiN diode with varying surge pulse width (5 μs~10 ms) and peak surge current up to 17.8 kA/cm2 following the IEC and JEDEC industrial standards.
In contrast with the clockwise hysteresis in the surge I-V locus of unipolar diodes, the anti-clockwise hysteresis in the surge I-V of the vertical GaN PiN diode, (along with its continuously reduced differential specific ON-resistance with time and current level) verifies the existence of the desired conductivity modulation and improved conduction during surge transients in the vertical GaN bipolar device.
For the first time, the mechanism and impact of the desired conductivity modulation on the surge current capability in direct-bandgap GaN device have been experimentally verified, which is fundamentally important to bipolar GaN devices for high power applications, according to the team.
The figures above show: (a) forward conduction and reverse blocking characteristics of the vertical GaN PiN diode. (b) Surge I–V characteristics with surge pulse width of 5 μs and peak surge current varying from 2 A to 16 A (17.6 kA/cm2) of the vertical GaN PiN diode. (c) Differential RON,sp as a function of surge current and surge pulse width varying from 5 μs to 10 ms. (d) Benchmark of breakdown voltage (BV) vs. Esurge of the state-of-the-art quasi- and fully-vertical GaN diodes.
Reference
‘Time-/Current-Dependent Surge Current Capability of Fully-Vertical GaN-on-GaN PiN Diode With Conductivity Modulation’ by Jiahong Du, Shu Yang et al; IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 12, no. 6, Dec. 2024.
