Deep traps in CdTe induced by ion implantation and annealing Original Research Article

The effects of In and Kr ion implantation and thermal annealing in n-type CdTe have been studied using Schottky barrier capacitance–voltage (C–V) measurements and deep level transient spectroscopy (DLTS). Using ion energies of 40–250 keV and doses of 1013–1016 cm−2, severe lattice damage was found in depths between 0.3 and 1.0 μm. While the damage was largely removed by mild annealing under vacuum (45 min at 200°C), such annealing treatment for both implanted and unimplanted samples resulted in the formation of a surface layer with reduced effective shallow donor concentration and the creation of trapping states at energy (Ec−0.15 eV). Both features were: (i) enhanced by successive vacuum annealing cycles at temperatures up to 450°C; (ii) suppressed by annealing under Cd vapour, instead of vacuum, thereby indicating that both effects can be attributed to the presence of Cd vacancies.