Identification of edge and exciton emission centres in CdTe

Photoluminescence from Ion Implanted CdTe Crystals

We have studied the photoluminescence of CdTe crystals doped with two elements, Cu and Cl, that are frequently used in CdTe-based solar cells. Ions were implanted into high-quality single crystals of CdTe at the Toledo Heavy Ion Accelerator Lab in our Department. We used a standard Monte Carlo simulation program to plan an implant dosage at three different energies. The lattice damage was removed by thermal annealing in an inert atmosphere using a proximity cap to avoid surface deterioration. The PL spectra at 40K were obtained at 488 nm or 752nm to match the absorption depth with the implant profile. Using implant densities typically of 1016, 1017, and 1018 /cm3, and laser excitation power densities ranging over several orders of magnitude, we have identified band-to-band transitions, free-to-bound transitions, bound-exciton lines, and donor-acceptor pair transitions related to these species.