High dose Cl implantation in ZnSe: Impurity incorporation and radiation damage

The structural characteristics of ZnSe thin films grown by organometallic vapor phase epitaxy and implanted heavily with Cl ions (5×10¹⁵ and 1×10¹⁶/cm²) were investigated using ion beam techniques, x-ray diffraction, and Raman spectroscopy. We have found that although the as-implanted ZnSe layers were severely damaged, no amorphous layer was formed with an implant dose as high as 1×10¹⁶ Cl ions/cm². Crystalline damage in the ZnSe layers was not fully removed even after annealing at 700 °C for 10 s. Ion channeling reveals that after annealing over 50% of the Cl atoms sit substitutionally in the lattice and they are preferentially located in the Se site. However, a significant fraction of the substitutional Cl are found to be slightly displaced from the normal Se sites. The projected displacement was found to be ≊0.2 Å. Electrical measurements and Raman spectroscopy results suggest that a large concentration of Zn vacancies (V_Zn) are present in the annealed samples. We believe that the Cl displacement and the low conductivity in these samples are due to the formation of (Cl_Se-V_Zn) complexes.