He+and N+ion irradiation of epitaxialp‐type In0.76Ga0.24As0.58P0.42and In0.53Ga0.47As was performed at 300 K to obtain high‐resistivity regions. In both the ternary and quaternary samples the resistivity first increases with ion dose. A maximum is reached at a critical dose depending on the ion species and initial doping concentration. Above this dose the conductivity converts tontype and the resistivity steadily decreases to ∼102&OHgr; cm in InGaAsP and ∼2 &OHgr; cm in InGaAs. After thermal annealing the type converted samples revert toptype. However, for ion doses ≥1013cm−2the high resistivities remain stable up to 700 K. The results suggest that simple point defects, rather than complexes are responsible for the changes in the electrical properties of the samples. ©1995 American Institute of Physics.