GaN-Based Vertical n-Channel MISFETs on Free Standing Ammonothermal GaN Substrates

E. Bahat-Treidel1, O. Hilt1, J. Stöver2, V. Hoffmann1, F. Brunner1, K. Ickert1, S. Hochheim1, F. Naumann3, H. Gargouri3, B. Martinez1, M. Weyers1, and J. Würfl1

Published in:

phys. stat. sol. (a), vol. 215, no. 8, pp. 1700422 (2018).

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Abstract:

In this work, a vertical n-channel MISFET homoepitaxially grown on ammonothermal n-type GaN substrates by MOVPE is demonstrated. The MIS gate module consists of plasma enhanced atomic layer deposition of Al2O3 combined with in-situ NH3 plasma surface pre-treatment. An annealing step performed at 350°C in N2 ambient drastically improves device performance. It reduces the ON-state resistance from ≈12.0 kΩ mm to ≈150 Ω mm, increases the ON-OFF ratio from 106 to 108, and lifts up Ids_max from ≈0.25 to ≈40 mA mm-1. The threshold voltage is above +5 V and the median vertical off-state blocking voltage strength is ≈68 V µm-1. Accumulated C-V characterization of planar MIS-capacitors on n-GaN gives insight to mechanisms boosting device performance after annealing.

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
2 Wroclawskie Centrum Badan EIT+ Sp. z o.o., ul. Stablowicka 147, 54-066 Wroclaw, Poland
3 SENTECH Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany

Keywords:

annealing, MISFET, normally-off, PEALD Al2O3, vertical GaN transistors.