CdCl2 treatment and its role in enhancing photodetection properties of CdTe and Cd1-xZnxTe films

Abstract

Close space sublimated CdTe and Cd_1-xZn_xTe (CZT) films were grown on glass substrates and CdCl₂ activation was applied on these films to improve their physical, optical and electrical characteristics for photodetector applications. X-ray diffraction data showed that CdCl₂ treatment of CdTe caused a reduction in the dislocation density and microstrain, whereas Zn incorporation/CdCl₂ treatment slightly increased these values compared to the as-deposited CdTe films. Morphological examination indicated that CdCl₂ activation transformed grains from faceted to rounded shape for both CdTe and CZT films. A band gap enlargement was observed from 1.45 eV to 1.47 eV for both CdTe and CZT films upon CdCl₂ treatment. CdCl₂-treated CZT films were used to fabricate photodetectors that exhibited the highest performance with a rise/fall time of 27/28 ms, sensitivity of 1301 %, responsivity of 0.0143 A/W, detectivity of 5.7x10⁷ Jones and external quantum efficiency of 4.0 % under blue light illumination at 2 V.