PL Study of Phosphorus-Doped CdTe EVT Films

Low temperature photoluminescence (PL) was used to study the effect of in-situ phosphorus (P) doping on polycrystalline Cadmium Telluride (CdTe) deposited by the Elemental Vapor Transport (EVT) technique. The CdTe films discussed in this paper were deposited under Cd/Te vapor ratios of 1.0, 2.0 and 3.0, and two vapor phase P concentrations of 4,000 and 16,000 ppm. Intensity and temperature dependent measurements revealed PL bands at 1.57, 1.50-1.56, 1.36-1.46, 1.28, 1.00 and 0.70 eV. It was determined that the 1.54 eV was due to transitions from donor to shallow acceptor states, likely P at Te vacancy (PTe). The 1.46 eV band was due to band to level transitions. Deep transitions around 1.00 and 0.70 eV were observed and are believed to be due to native defects.