Investigation on ZnTe/Cd_xZn_1-xTe heterostructure for photodetector applications

ZnTe/Cd_xZn_1-xTe (0.2 ≤ x ≤ 1.0) heterostructures were fabricated by thermal evaporation method by using CdTe and ZnTe as source materials. The properties of heterostructures were analysed by X-ray diffraction (XRD), photoluminescence (PL), temperature dependent Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and I-V characterizations. Double diffraction peak in the diffractogram has confirmed bilayer with no or minimum diffusion across the junction. Effect of thermal expansion and an-harmonic coupling to the other phonon modes causing strain induced shift of the longitudinal optical modes were studied through low-temperature Raman spectra. The junction parameters such as barrier height, ideality factor and series resistance were extracted from I - V characteristics by applying various models. ZnTe/Cd_xZn_1-xTe heterostructures having low barrier height and good photo response are explored in this work for the photodetector application. Sample having composition x = 0.8 showed higher response in the visible region with improved response at longer wavelengths.