Investigation of interlayer role of SLp biomaterial synthesized by a sol-gel method for bioelectronic applications: hybrid photodiode

In this study, a n-Si based photodiode was fabricated to investigate the electrical role of a surface layer protein (SLp)-interlayer, which is a biomaterial, for the first time. The SLp material extracted from the Lpb. plantarum strain was analyzed and found to have a molecular mass of 54 kDa. The Raman spectrum of the SLp thin film showed the existence of specific secondary component vibration bands associated with β-sheet, α-helix, β-turns and antiparallel β-sheet. The Schottky photodiodes were constructed with and without an SLp-interlayer, named SID and RFD. The thickness of the interlayer is ~190 nm. The best RFD and SID diodes have n and ϕ_B of 1.75, 0.663 eV and 1.95, 0.737 eV, respectively. The rectification ratio is ~10 times greater for the SLp-interlayered photodiode. In the dark conditions, the SLp-interlayered photodiode has lower leakage current ( ~ 10⁻⁸A) and higher rectification ratio ( ~ 10⁴). Furthermore, the N_ss value decreased from 10¹⁵eV⁻¹cm⁻² to 10¹³eV⁻¹cm⁻² with shifting distribution from E_c-0.52 eV to E_c-0.64 eV. Photo-characterization was carried out under light having irradiance values ranging from 10 to 100 μW/cm² (629 nm, 515 nm, 456 nm). The SLp-interlayered photodiode has higher and stabile detectivity (2.67 × 10¹⁰ Jones), lower noise-equivalent power (0.495 pWHz^−0.5) and bistable switching (on/off ~1,5 × 10²) at on-position. The performance parameters revealed that the SLp-interlayered devices can be used for optoelectronic applications under low incident optical power (μW), especially for bio-electronic applications such as biosensors which are biologically compatible with the human body. This bio-hybrid approach opens a new pathway in optoelectronic device engineering by combining the molecular precision of biological systems with the robustness of semiconductor technology.

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