Author:
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Perez-Tomas, Amador; Catalan, Gustau; Fontserè Recuenco, Abel; Iglesias Santiso, Vanessa; Chen, H.; Gammon, Peter; Jennings, M. R.; Thomas, M.; Fisher, C. A.; Sharma, Y. K.; Placidi, Marcel; Chmielowska, M.; Chenot, S.; Porti i Pujal, Marc; Nafría i Maqueda, Montserrat; Cordier, Y.
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Abstract:
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The gallium nitride (GaN)-based buffer/barrier mode of growth and morphology, the transistor electrical response (25-310°C) and the nanoscale pattern of a homoepitaxial AlGaN/GaN high electron mobility transistor (HEMT) have been investigated at the micro and nanoscale. The low channel sheet resistance and the enhanced heat dissipation allow a highly conductive HEMT transistor (Ids > 1 A mmˉ¹) to be defined (0.5 A mm¯¹ at 300 °C). The vertical breakdown voltage has been determined to be ~850 V with the vertical drain-bulk (or gate-bulk) current following the hopping mechanism, with an activation energy of 350 meV. The conductive atomic force microscopy nanoscale current pattern does not unequivocally follow the molecular beam epitaxy AlGaN/GaN morphology but it suggests that the FS-GaN substrate presents a series of preferential conductive spots (conductive patches). Both the estimated patches density and the apparent random distribution appear to correlate with the edge-pit dislocations observed via cathodoluminescence. The sub-surface edge-pit dislocations originating in the FS-GaN substrate result in barrier height inhomogeneity within the HEMT Schottky gate producing a subthreshold current. |