Deep-level photoluminescence emissions in the 1.1eV spectral region of polycrystalline samples of p-type Cl-doped material was studied as a function of laser excitation power and temperature. It was found that the relatively broad 1.1eV photoluminescence band had a non-symmetrical shape which could be easily changed by varying the excitation laser power. Detailed analysis of the line-shape showed that the 1.1eV emission comprised 2 distinct separate bands. These 2 bands had zero-phonon peaks which were located at 1.08 and 1.17eV, and had quite different half-widths. A donor-acceptor pair model with a deep donor and a deep acceptor, with energies that were both greater than 0.5eV, was proposed in order to explain the experimental results. In this model, the 1.08 and 1.17eV bands formed due to donor-acceptor recombination between pairs of nearest neighbors, and between pairs of next-nearest neighbors, respectively. It was concluded that the acceptor in these pairs was an interstitial atom. One possible form for this type of donor-acceptor pair was a VTe-Tei complex; where VTe acted as a donor and Tei acted as an acceptor.

J.Krustok, V.Valdna, K.Hjelt, H.Collan: Journal of Applied Physics, 1996, 80[3], 1757-62