Ion-implantation induced optical absorption edge shifts in GaP

The effects of implantation of argon on the optical properties of GaP films and bulk have been investigated for doses of 1013 to 1015/cm2 and energies between 1.5 and 3 MeV. Implantation of ordered films and bulk GaP results in a marked change in the optical absorption edge from about 2.3 eV to less than 1.0 eV, similar to behavior observed for amorphous films and for those subject to neutron irradiation. A maximum value of 3.22 has been observed for the index of refraction of implanted films as compared with 3.06 for bulk or highly ordered films. Bulk optical behavior can be recovered for implanted GaP with annealing at temperatures below 600°C.