POSITON ANNIHILATION AT VACANCIES IN HG0.8CD0.2TE CRYSTALS AFTER ELECTRON-IRRADIATION

Accepters and vacancy-type defects have been investigated in traveling -heater-method-grown Hg(0.8)Cdo(0.2)Te crystals by measuring the posit ron lifetime after 2.5-MeV electron irradiation in liquid hydrogen and annealing from 77 to 340 K. The results give evidence that negative V -Hg vacancies are introduced. They disappear slowly at room temperatur e over several weeks. Another monovacancy is also observed when the Fe rmi level is high in the gap. It is tentatively identified with the V- Te vacancy. A recovery stage is observed between 150 and 280 K, the na ture of which is discussed.