Photoluminescence of deep level complexes in CdTe

Abstract

An inevitable property of CdTe detector-grade material is a high resistivity at room temperature. Chlorine doping is a classical method to control compensation mechanisms for reaching the high resistivity material. An alternative process has been shown to be a suitable indium-doping. Additional post-growth annealing in Cd- and Te-vapour overpressure was used to obtain high resistivity material. Low temperature photoluminescence spectra were measured. The luminescence was excited either by a red laser or by a tunable Ti-sapphire laser. A typical photoluminescence line at 1.584 eV dominates the high energy end of the luminescence spectra for high resistivity material. Several low intensity luminescence bands due to shallow (effective mass) acceptors and a relatively intensive band with well-developed optical phonon replicas connected with A-centres (complex of Cd vacancy and donor atom) were observed with zero-phonon line at 1.450 eV. In the low energy part of the measured spectral range (<1.3 eV), not only common weak and very broad luminescence bands without phonon replicas structure were apparent, but also an unusual band with clearly resolved phonon structure with zero-phonon line at 1.287 eV. A defect similar to the A-centre could be responsible for this structure.