Infrared PL studies of sputtered CdTe films and cells

Photoluminescence (PL) in CdTe in the range from 0.7 eV to 1.5 eV provides a great deal of information about shallow and deep defects and the role of CdCl₂ activation treatments in changing the density of these defects. We have used an InGaAs diode-array detector to study this region at 10 K in as-sputtered films and CdCl₂-treated films. In the region from 0.7 to 1.2 eV we find a series of peaks from deep donor-acceptor pairs that is quite sensitive to the sputter deposition conditions in the range of pressures from 2.5 mTorr to 30 mTorr. In the near-band-edge region from 1.3 to 1.5 eV, studied from the contact side of cells, we find PL peak shifts indicative of some S alloying at the back surface as the chloride activation time increases.