Journal Article Current linearity and operation stability in Al2O3-gate AlGaN/GaN MOS high electron mobility transistors

Nishiguchi, Kenya  ,  Kaneki, Syota  ,  Ozaki, Shiro  ,  Hashizume, Tamotsu

56 ( 10 )  , pp.101001-1 - 101001-8 , 2017-10 , IOP Publishing
To investigate current linearity and operation stability of metal-oxide-semiconductor (MOS) AlGaN/GaN high electron mobility transistors (HEMTs), we have fabricated and characterized the Al2O3-gate MOS-HEMTs without and with a bias annealing in air at 300 degrees C. Compared with the as-fabricated (unannealed) MOS HEMTs, the bias-annealed devices showed improved linearity of I-D-V-G curves even in the forward bias regime, resulting in increased maximum drain current. Lower subthreshold slope was also observed after bias annealing. From the precise capacitance-voltage analysis on a MOS diode fabricated on the AlGaN/GaN heterostructure, it was found that the bias annealing effectively reduced the state density at the Al2O3/AlGaN interface. This led to efficient modulation of the AlGaN surface potential close to the conduction band edge, resulting in good gate control of two-dimensional electron gas density even at forward bias. In addition, the bias-annealed MOS HEMTshowed small threshold voltage shift after applying forward bias stress and stable operation even at high temperatures.

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