MBE-grown ZnTe epitaxial layer based broadband photodetector with high response and excellent switching characteristics

Abstract

Zinc telluride (ZnTe) epitaxial layers were grown on gallium arsenide (GaAs) (211) substrate at different growth temperatures by molecular beam epitaxy (MBE). The fabricated interdigitated metal semiconductor metal (MSM) configuration-based photodetector on ZnTe epitaxial layers exhibited stable and excellent photo response in a broad spectral range (250 to 550 nm) up to 125 ℃. The room temperature and higher temperature (125 ℃) values of maximum current, spectral responsivity, and detectivity at an applied bias of 5 V and 550 nm wavelength were 3.5×10-8 A, 0.1 A/W and 1×1011 Jones and 1.7×10-6 A, 2.5 A/W and 1.5×1011 Jones, respectively. The maximum photo-to-dark-current ratio (PDCR) value at zero bias and 100 ℃ was obtained for the ZnTe layer grown at an optimum growth temperature of 380 ℃. The high PDCR value exhibits the self-powered capability of the detector. Further, the detector exhibits good On-Off switching to the illuminating light with rise and decay times less than 0.29 s and 0.4 s, respectively, at room temperature. The dependence of photo response on material quality was analysed by varying the substrate growth temperature. The broadband responsivity of the ZnTe-based photodetector shows its capability as a multicolour detector in UV and visible region with the use of suitable blocking filters.