Exploration of photoresponsivity, specific detectivity and interface properties of Au/ZnPc/InP/In photodiode at different illumination wavelengths

This work explores the interface properties of Au/zinc phthalocyanine (ZnPc)/InP/In photodiode (PD) under dark and different illumination wavelengths. Bias-dependent properties of the PD such as photo-to-dark current ratio, photoresponsivity and specific detectivity (D*) were evaluated for the illumination wavelength from 400 to 1000 nm in steps of 20 nm. The photoresponsivity and D* appear superior for specific wavelengths, such as 640, 680, 740, 780, 860 and 960 nm. The barrier properties of the PD were analysed for these selective wavelengths. Variation of barrier parameters under illumination at different wavelengths signifies the generation of photo carriers that influence the photocurrent, which alters the series and shunt resistance of the junction. The barrier parameters were also evaluated using the thermionic emission model, Cheung's and Norde's methods. The magnitude of barrier parameters obtained using these approaches shows their consistency and validity. The density of states distribution was obtained from the forward bias photocurrent–voltage curves for dark and selective illumination wavelengths. The current transport processes of PD were explored under both forward and reverse bias conditions in dark and different illumination wavelengths. Analysis indicates that ohmic and space charge limited current processes in the forward bias of PD are present in both dark and illumination conditions. Additionally, it was found that Poole-Frenkel emission governs at lower bias, while Schottky emission governs at higher bias regions in the reverse bias of PD in both dark and illumination conditions.