Cross section TEM image of the AlGaN/GaN sample after annealing in at for 2 (a) and 12 h (b).The dashed line indicates the position of the AlGaN/GaN heterointerface. Clearly, the formation of a surface oxide layer did not result in the consumption of the AlGaN/GaN heterointerface.
(a) Cross section TEM image of the AlGaN/GaN sample after annealing in at for 2h in the proximity of a defective region. (b) Oxygen map determined by EFTEM, indicating the preferential oxidation of the defects.
Top: schematic of the test patterns used for electrical characterization of the isolation. Bottom: characteristics measured in the isolated test pattern and in the reference.
(a) Surface morphology acquired on the area including the selectively oxidized frame reported for the sample annealed at for 12 h. (b) Linescan of the measured height vs the lateral position along the dashed line in (a). (c) Current map acquired by C-AFM measuring the current between the nanometric AFM tip and a biased macroscopic Ohmic contact on the AlGaN epilayer external to the frame. (d) Schematic illustration of the scanned area.
characteristics of HEMT devices fabricated on the as-grown material and on the sample annealed at . During annealing the sample was protected by a capping layer.
(a) curves of HEMT devices fabricated on the as-grown material and on the sample annealed at (during annealing the sample was protected by a capping layer). (b) Sheet carrier density as a function of the gate bias, determined from the curves.
(Top) Schematic of the AlGaN/GaN heterostructure. (Bottom) SCM profile taken in the nonoxidized region and in the oxidized region.
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