Investigations on optical behavior of Crystalline-Ge ₂ Sb ₂ Te ₅ for photo-detection application in near infra-red region

Present work reveals the investigations done on crystalline Ge ₂ Sb ₂ Te ₅ (c-GST) based vertical photodetector for telecommunication wavelength (1550 nm) by optimizing the device dimensions on Silicon platform. Simulation studies done for the optimized structure reveal that the c-GST can be the promising material for the photo-detection applications. In our investigations, ∼210 nm is found to be the optimized thickness for c-GST with highest ∼63 A/W responsivity at 1150 nm when integrated on a single mode silicon-on-insulator (SOI) waveguide. The responsivity of ∼41 A/W is observed at 1550 nm of wavelength. A comparative analysis is also done with the amorphous GST (a-GST). A shift of 100 nm wavelength towards the higher side is observed for c-GST which may be due to its lower bandgap. Minimum detectable power (P _min ) and noise equivalent power (NEP) of the proposed device is calculated and found to be 0.19 μW and 28.76 fW/Hz ^1/2 at 43.1 THz bandwidth, respectively.