Comparative analysis of chloride-treated ZnTe films in photodetector devices

Abstract

The current work aims to demonstrate the potential effects of different Cl-treatments on ZnTe thin films as candidates for photodetector applications. X-ray diffraction (XRD) data revealed that the degree of preferred orientation along the (111) plane increased with Cl-treatments compared to the as-deposited ZnTe, and Cl-treatment also promoted crystal growth in ZnTe. Surface images showed that the MgCl2-treated ZnTe sample exhibited a transformation of faceted grains into rounded shapes, resulting in a denser and more compact microstructure. Among the samples, the CdCl2-treated ZnTe demonstrated a sharper transition. The optical band gaps were 2.18 eV for the as-deposited ZnTe film, 2.16 eV for the ZnCl2-treated sample, 2.20 eV for the CdCl2-treated sample, and 2.19 eV for the MgCl2-treated sample. This indicates that ZnCl2 treatment slightly lowers the band gap, whereas CdCl2 and MgCl2 treatments lead to small increases. The current-voltage (I-V) curves displayed a steeper slope under both dark and illuminated conditions after ZnCl2, MgCl2, and CdCl2 treatments compared to the as-deposited ZnTe, likely due to enhanced conductivity. The CdCl2-treated ZnTe photodetectors (PDs) exhibited the fastest photoresponse, with rise and fall times of 13 m s each. Furthermore, CdCl2-treated ZnTe-based PDs achieved the highest sensitivity (S = 417 %), responsivity (R = 0.0024 A/W), and detectivity (D∗ = 1.4 × 107 Jones) among the tested devices, suggesting that these PDs are suitable candidates for high-performance photodetector applications.