Co-doping of Mn and Cr in CdTe thin films: Tunable white light emission and structural stability

Abstract

Mn and Cr co-doped CdTe thin films were synthesized using the radio frequency (RF) sputtering technique on (001) GaAs substrates. Comprehensive investigations were conducted to evaluate the structural, morphological, vibrational, and optical properties of the resulting films. X-ray diffraction (XRD) analysis confirmed that the doped CdTe thin films retained a cubic zinc blende crystal structure, indicating the successful incorporation of Mn and Cr ions into Cd lattice sites. Surface morphology and elemental composition were assessed through high-resolution scanning electron microscopy (HR-SEM) and energy-dispersive X-ray spectroscopy (EDS) mapping. The films exhibited a smooth, uniform morphology, which remained consistent across varying dopant concentrations, signifying stable film growth. Fourier-transform infrared (FTIR) spectroscopy was employed to identify functional groups present in the films, while Raman spectroscopy provided insights into the intrinsic vibrational modes associated with the CdTe lattice. Photoluminescence (PL) measurements revealed characteristic blue and green emission bands, with prominent peaks observed at 433 nm and in the 512–525 nm range, respectively. The peak shifting corresponds to the energy transitions involving Mn²⁺ and Cr²⁺ dopant levels. The Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates for the Mn-doped CdTe films were determined to be (0.30, 0.33), closely approximating pure white light emission. The co-doped films displayed white light emission with a subtle blue shift, and the corresponding correlated color temperature (CCT) was calculated to exceed 5000 K, situating the emission in the cool white light region. These results suggest that Mn, Cr co-doped CdTe thin films possess significant potential for use in optoelectronic devices, particularly in light-emitting diode (LED) applications.