Processing Methods for Low Ohmic Contact Resistance in AlN/GaN MOSHEMTs

K. Chabak, A. Crespo, D. Tomich, D. Langley, V. Miller, M. Trejo, J.K. Gillespie, G.D. Via Sensors Directorate, Air Force Research Laboratory Wright-Patterson Air Force Base, Ohio 45433

A.M. Dabiran, A.M. Wowchak, B. Cui, P.P. Chow SVT Associates, Inc. Eden Prairie, Minnesota 55344

Keywords: AlN, HEMT, MOSHEMT, ALD, Ohmic Contacts

ABSTRACT

In this work, we demonstrate various ohmic contact formation processes using an AlN/GaN (MOS)HEMT structure with an aluminum oxide gate dielectric formed by ALD. The MOSHEMT structure is advantageous because the thin oxide layer protects the ultra-thin (~3 nm) AlN barrier against exposure to the processing chemicals. Contact resistance values as low as

0.457 Ω·mm are reported on TLM structures. The corresponding devices exhibited excellent electronic transport properties with room temperature mobility µ > 1000 cm2/V·s and sheet carrier concentration nS > 3.25 x 1013 cm-2. These are the lowest contact resistance values obtained for AlN/GaN HEMTs in the high mobility range (> 1000 cm2/V·s).

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