Fabrication of p-ZnCo2O4/n-Si spinel heterojunction devices for self-powered ultraviolet photodetectors: Effect of Zn2+concentration

Pure and zinc-doped cobalt oxide heterojunction devices on n-type silicon substrates have been fabricated via sol-gel spin coating deposition. The fabricated devices have been characterized by XRD, Raman spectroscopy, FESEM, and EDS elemental mapping. The fabricated heterojunction devices show non-linear I-V characteristics, which suggests their diodic behavior. A blend of mathematical and physical methods that are based on the Lambert W function and the modified Shockley equation has been used to examine the performances of the devices. The UV sensing measurements were conducted on the devices under zero bias conditions while they were subjected to UV light with wavelengths of 365 and 254 nm. The study has indicated that Co3O4 in its pure form does not exhibit activity towards either UV wavelength. However, the introduction of Zn2+ into Co3O4 results in a notably substantial photoresponse of approximately 978 %, 1393 %, and 2400 % for Zn2+ concentrations of 5 %, 15 %, and 30 %, respectively, when exposed to 365 nm UV radiation. The responsivity value of the fabricated devices was found to increase from 0.026 mA/W to 15.82 mA/W with an increase in Zn2+ from 5 % to 30 %. Detectivity and EQE values of the devices also demonstrate remarkable increase from 7.50 x 108 cmHz1/2/W (5 % Zn2+) to 2.86 x 1010 cmHz1/2/W (30 % Zn2+) and from 0.009 % (5 % Zn2+) to 5.39 % (30 % Zn2+) respectively. The increase in Zn2+ concentration also increases the linear dynamic range (LDR) value from 20.65 dB to 27.96 dB.

Automated summary

Pure and zinc-doped cobalt oxide heterojunction devices have been fabricated on n-type silicon substrates using sol-gel spin coating deposition. The introduction of Zn2+ into Co3O4 results in a substantial increase in the photoresponse, detectivity, EQE values, and linear dynamic range (LDR) of the devices.