N-type layers of InxAl1-xN and InxGa1-xN were implanted with multiple energy N+, F+, or O+ ions at doses in the range 5 X 10(12)-5 X 10(14) Cm-2, and subsequently annealed up to 900 degrees C. Increases in sheet resistance of up to factors of similar to 10(4) were achieved in In0.75Al0.25N after implantation at the higher doses, followed by annealing at 600-700 degrees C. The behavior for Ln(x)Ga(1-x)N followed the same trend, with somewhat lower increases in sheet resistance. The implantation creates deep acceptor states in the upper part of the band gap of both types of material, rather than at midgap, which is the optimum situation for implant isolation.