DC and RF Performance of AlN/GaN MOS-HEMTs

Sanna TAKING  Douglas MACFARLANE  Ali Z. KHOKHAR  Amir M. DABIRAN  Edward WASIGE  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.5   pp.835-841
Publication Date: 2011/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.835
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Fundamentals and Applications of Advanced Semiconductor Devices)
Category: 
Keyword: 
AlN/GaN,  HEMT,  MOS-HEMT,  Al2O3,  wet etching,  thermal oxidation,  small-signal model,  

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Summary: 
This paper reports the DC and RF characteristics of AlN/GaN MOS-HEMTs passivated with thin Al2O3 formed by thermal oxidation of evaporated aluminium. Extraction of the small-signal equivalent circuit is also described. Device fabrication involved wet etching of evaporated Al from the Ohmic contact regions prior to metal deposition. This approach yielded an average contact resistance of ∼0.76 Ω.mm extracted from transmission line method (TLM) characterisation. Fabricated two-finger AlN/GaN MOS-HEMTs with 0.2 µm gate length and 100 µm gate width showed good gate control of drain currents up to a gate bias of 3 V and achieved a maximum drain current, IDSmax of ∼1460 mA/mm. The peak extrinsic transconductance, Gmax, of the device was ∼303 mS/mm at VDS = 4 V. Current-gain cut-off frequency, fT, and maximum oscillation frequency, fMAX, of 50 GHz and 40 GHz, respectively, were extracted from S-parameter measurements. For longer gate length, LG = 0.5 µm, fT and fMAX were 20 GHz and 30 GHz, respectively. These results demonstrate the potential of AlN/GaN MOS-HEMTs for high power and high frequency applications.