Fabrication of highly responsive phase-change GeSbTe photodetector for visible region

In the present work, GeSbTe (GST) material is investigated for detection in visible range (specifically at 632 nm wavelength) for spectroscopic photodetection and visible-light communication applications. Thin film of GST phase-change chalcogenide material was deposited by RF sputtering method and thickness was optimized by varying the RF power and deposition time. The deposition was done on Si and glass substrate, individually. Phase-change property was observed by heating the material in the ambient atmosphere. There was approximately two times change is resistance at ~ 90 °C. The films were found to possess the FCC and hexagonal structure using X-ray diffraction in the crystalline form. The complex refractive indices were obtained using spectroscopic ellipsometry in the visible range. The absorbance spectrum of each film was also recorded. The deposited material found to have absorption coefficient (α) in order of ~ 10 in the visible range which is showing the potential of photodetection in the visible range. Photodetection of GST thin film in four different structures (Metal–Semiconductor and Metal–Semiconductor–Metal on Si and Glass) were analyzed under the illumination of 632 nm, ~ 8 mW/cm laser and 530 nm, ~ 1 mW/cm halogen light in 1 V electrical biasing. The responsivity of higher than 1 A/W has been observed. A detailed comparison is done between dark current and photo-current for various structures, thicknesses and materials (amorphous and crystalline). For a glimpse of the speed of the fabricated device, the on/off-transient has been performed, and a 0.3 s response time and 0.15 s decay time have been found. A detailed comparison is also presented here with the other fabricated devices within same application range for the viability of the reported work.