Optoelectronic properties of undoped and N-doped ZnTe films grown by RF sputtering: Effect of the substrate temperature and N nominal concentration

Undoped and N-doped ZnTe films were deposited by RF magnetron sputtering. Undoped ZnTe films were grown varying the substrate temperature, while N-doped ZnTe films were obtained at 360 degrees C with different N nominal concentrations. The XRD and HR-TEM results showed that ZnTe and Te phases coexist in undoped and N-doped ZnTe films. Raman analysis showed the presence of signals associated with tellurium-rich phases as well as the mode of Zn-Te bond. The incorporation of N in the ZnTe films was corroborated through XPS measurements. The optical characterization showed that the increase in N nominal concentration in the ZnTe lattice reduces the bandgap from 2.38 eV (undoped) to 1.48 eV for the highest nominal N content. The electrical characterization showed that doping with nitrogen reduces the resistivity in four orders of magnitude. CdS/CdTe solar cells were fabricated using undoped and N-doped films to evaluate their performance through the J-V curves.