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Normally-off High-Voltage p-GaN Gate GaN HFET with Carbon-Doped Buffer
O. Hilt, F. Brunner, E. Cho, A. Knauer, E. Bahat-Treidel and J. Würfl
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
Published in:
Proc. Int. Symp. on Power Semiconductor Devices & IC's (ISPSD), San Diego, CA, May 23-26, pp. 239-242 (2011).
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Abstract:
Normally-off GaN transistors for power applications
in p-type GaN gate technology with a modified carbon-doped
GaN buffer are presented. A combination of an AlGaN backbarrier
with the carbon-doped buffer prevents early off-state
punch-through. Simultaneously, the on-state resistance could be
kept low and the threshold voltage with 1.1 V high enough for
secure normally-off operation. 1000 V breakdown strength has
been obtained for devices with 6 µm gate-drain spacing. The
resulting breakdown scaling slope is 170 V/µm gate-drain
distance. The on-state resistance is 7.4 Ωmm. The resulting VBrto-
RONA ratio (1000 V, 0.62 mΩcm2) is beyond so far reported
ratios for normally-off GaN transistors. Modifications of the ptype
GaN layer have shown to additionally increase the
threshold voltage by 0.4 V without paying a price in the on-state
resistance of the device.
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