Comparison of Implant Isolation Species for GaN Field-effect Transistor Structures

Different ions (Ti + , O + , Fe + , Cr + ) were implanted at multiple energies into GaN field effect transistor structures (n and p-type). The implantation was found to create deep states with energy levels in the range E C −0.20 to 0.49 eV in n-GaN and at E V +0.44 eV in p-GaN after annealing at 450-650 °C. The sheet resistance of the GaN was at a maximum after annealing at these temperatures, reaching values of ∼4×10 12 Ω/□ in n-GaN and ∼10 10 Ω/□ in p-GaN. The mechanism for the implant isolation was damage-related trap formation for all of the ions investigated, and there was no evidence of chemically induced isolation.