The influence of ion‐irradiation damage on the electrical properties of Hg0.79Cd0.21Te has been investigated. A large damage‐inducedn‐type conductivity with sheet carrier concentration up to approximately 1014cm−2and sheet resistance up to 10 &OHgr;/square at 77 K was found for doses of 1×1015ions/cm2at 150 keV. The observedn‐type conductivity is produced by various implanted ions regardless of whether they are donors or acceptors. The implantedn‐type layer maintains its properties when subjected to temperatures as high as 120 °C. The damage is slightly annealed for this moderate treatment: the conductivity increases slightly, the sheet electron concentration decreases, and the effective mobility increases. The results also show that the implanted layer can be utilized for surface passivation ofn‐type photoconductors and for making Ohmic contacts ton‐type material.