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Current aperture vertical electron transistor (CAVET) was successfully demonstrated by using Mg-implanted GaN as a current blocking layer for nonalloyed source contacts. A maximum source-drain current of (corresponding to 0.22 A/mm of source) and an extrinsic transconductance of 54 mS/mm of source were achieved. Threshold voltage as high as 0.6 V was realized by plasma exposure for 10 min, increasing the transconductance of the device to 140 mS/mm of source. Thus, a normally off CAVET was demonstrated for the first time. The increase in by plasma exposure for a given bias was due to etching of the AlGaN barrier. The shift of threshold voltage and the varied directly with the time of exposure. There was no significant dispersion in these devices.
Date of Publication: June 2008