Improved Vertical Isolation for Normally-Off High Voltage GaN-HFETs on n-SiC Substrates

O. Hilt, P. Kotara, F. Brunner, A. Knauer, R. Zhytnytska, and J. Würfl

Published in:

IEEE Trans. Electron Devices, vol. 60, no. 10, pp. 3084-3090 (2013).

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Argon implantation of n-type SiC substrates prior to epitaxial growth of AlGaN/GaN HFETs stacks is used to decrease the vertical leakage to the conductive substrate. Normally-off p-GaN gate transistors with AlGaN-buffer and with iron-doped GaN-buffer were analyzed. The device OFF-state drain leakage was reduced for high drain voltages >400 V and the maximum breakdown strength was increased from 520 to 880 V for iron-doped GaN-buffer devices. Static device characteristics and the dynamic ON-state resistance of devices fabricated on pre-implanted SiC substrates are not degraded. High Resolution X-ray Diffraction (HRXRD) analysis confirms in coincidence that the GaN buffer defect density is not increased. Substrate implantation is thus beneficial for low-leakage high-voltage GaN devices on n-type SiC substrates.

Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany

Index Terms:

Aluminum gallium nitride, breakdown, HEMTs, power transistors.