Ion implantation for isolation of AlGaN/GaN HEMTs using C or Al

In this work, we report on the fabrication of electrical isolation for planar AlGaN/GaN high electron mobility transistors (HEMTs) using Al and C ion implantation. Our methodology was to maintain uniform vacancy concentration (>4x10(20)cm(-3)) up to the depth of 0.7 mu m for both ion species. Electrical measurements have shown that after implantation, the sheet resistance was 1x10(11)/ and increased to 5x10(13)-1x10(14)/ after annealing at 400 degrees C and to 5x10(12)-1x10(13)/ after annealing at 600 degrees C. Further annealing at 800 degrees C decreased the sheet resistance to 5x10(7)/ and 1x10(8)/, respectively for C and Al implantation. Characterization by XRD, Raman and photoluminescence spectroscopy provides evidence that implantation damages the crystal lattice, yielding insulating properties. It is demonstrated that the isolation is stable up to 600 degrees C. We also demonstrate AlGaN/GaN HEMTs on semi-insulating Ammono-GaN substrates working both in DC (I-DS=800mA/mm) and RF (up to 6.5GHz) mode with isolation prepared by means of the described approach.