Performance evaluation of multi layered ZnO/Ge/Si photodetector: the effect of pulses laser

Triple-layer heterostructure of ZnO/Ge/Si was considered for establishing photodetector devices by utilizing thermal evaporation and pulse laser deposition. The structural and optical properties were obtained using XRD, SEM, Raman spectroscopic and UV–visible spectroscopy. The XRD showed patterns of the Ge layer a closed-oriented crystalline structure and results showed that zinc oxide is polycrystalline in nature, with a cubic crystalline phase. The Raman spectroscopic investigation of Ge film the figure shows three separate peaks, In particulars are corresponded to Ge phase, E(TO + LO), A1(TO), E(TO)respectively and the Raman spectra of ZnO films showed E (LO), A (TO), E (LO) + TO, and B1 vibration modes. The optical bandgaps of Ge and ZnO nanostructures were found to be 2.8 for Ge and 3.3, 3.2, and 3.1 eV for ZNO thin film as laser pulses of 400, 500, 600 pulses respectively. The current–voltage characteristics of the ZnO/Ge/Si heterojunction deposited over 400, 500, and 600 pulses were examined in dark and illumination condition. Using more pulse lasers improved the photodetector performance and the figure of merit. When the deposition pulse was increased from 400 to 600 pulses, the responsivity increased from 8.867 to 13.229 µA/W. When the photodetector was produced at the ideal pulse count of 600 pulses, the detectivity (D*) and external quantum efficiency (EQE) were 5.77 × 10¹⁴ Jones and 40.505%, respectively, at 405 nm.