Vertical GaN-on-GaN Schottky Barrier Diodes With Multi-Floating Metal Rings

Tsung-Han Yang,Xin Qi,Houqiang Fu,Jossue Montes,Kai Fu,Yuji Zhao,Jingan Zhou,Xuguang Deng,Xuanqi Huang,Chen Yang,Hong Chen

doi:10.1109/jeds.2020.3014133

Tsung-Han Yang, Xin Qi + Show 9 more

Open Access

https://doi.org/10.1109/jeds.2020.3014133

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Abstract

Vertical GaN Schottky barrier diodes (SBDs) with floating metal rings (FMRs) as edge termination structures have been fabricated on bulk GaN substrates. Devices with different FMR geometries were investigated including various numbers of rings and various spacings between rings. These devices have a low Ron of 1.16~1.59 mΩ·cm 2 , a turn-on voltage of 0.96~ 0.94 V, a high on-off ratio of 10 9 , a nearly ideal ideality factor of 1.03~1.09, and a Schottky barrier height of 1.11~1.18 eV at room temperature. These devices have similar forward electrical characteristics, indicating that FMRs don't degrade the device rectifying performance. The ideality factor decreased and the Schottky barrier height increased with increasing temperature from 300 K to 420 K, where the temperature dependencies of the two parameters indicate the inhomogeneity of the metal/semiconductor Schottky interface. In addition, FMRs can improve device breakdown voltages. As the number of FMRs increased from 0 to 20, the reverse breakdown voltage increased from 223 to 289 V. As the spacing between the FMRs increased from 1.5 to 3 μm, the reverse breakdown voltage increased from 233 to 290 V, respectively. These results indicate multiple FMRs with proper spacings can effectively improve breakdown performance without degrading the device forward characteristics. This work represents a useful reference for the FMR termination design for GaN power devices.

Highlights

Gallium nitride has been widely used in both electronic and photonic devices [1]–[7]
The specific on-resistances extracted from the curves were about 1.47, 1.37, 1.16, 1.59 m ·cm2, respectively. These results indicate that the addition of floating metal rings (FMRs) doesn’t significantly impact the device forward rectifying characteristics
Vertical GaN Schottky barrier diodes with various FMR structures were fabricated on bulk GaN substrates

Summary

INTRODUCTION

Gallium nitride has been widely used in both electronic and photonic devices [1]–[7]. Conventional lateral GaN power devices have been grown and fabricated on foreign substrates such as sapphire [8], [9] and silicon [4], [10]–[12], which showed limited performance This is because lateral geometry results in surface-related issues, poor thermal dissipation, and limitations on current and voltage ratings. YANG et al.: VERTICAL GaN-ON-GaN SCHOTTKY BARRIER DIODES WITH MULTI-FLOATING METAL RINGS main Schottky junction due to the expansion of the depletion layer along the FMRs [26]. This method has been adopted in SiC [26], [27] and Ga2O3 [28] Schottky barrier diodes. These results can serve as helpful references for the future development of power GaN devices

DEVICE FABRICATION

RESULTS AND DISCUSSION

CONCLUSION