Wejdan S. AlGhamdi

Within multijunction organic and hybrid photodetectors (PDs), organic and hybrid phototransistors (HPTs) hold promises for high sensitivity (S) and specific detectivity (D*). However, it is difficult to achieve a trade‐off between a large sensing area, a fast response, and a high D*. Here, we propose an alternative phototransistor concept relying on a geometrically engineered tri‐channel (Tr‐iC) architecture with a 4‐mm ² large sensing area, applied to a multilayer HPT whose active region is comprised of an inorganic In ₂ O ₃ /ZnO n‐type field‐effect channel and solution‐processed organic bulk heterojunction (BHJ) or hybrid perovskite light‐sensing layer. The resulting HPTs combine a responsivity (R) up to 10 ⁵ A/W, thanks to the efficient charge transport (at the bottom In ₂ O ₃ /ZnO layer) and a D* estimated at 10 ¹⁵ Jones, which allows to measure low light power densities down to 10 nW cm ⁻² . These figures of merit are coupled to a fast response (risetime 2 range), which is comparable to the time‐response of organic PDs in a diode architecture. The experimental data are supported by a comprehensive device modeling, which helps highlighting the peculiar advantages of the proposed large area, Tr‐iC, and multilayer HPT architecture.

Combining low-dimensional layers of dissimilar metal oxide materials to form a heterojunction structure offers a potent strategy to improve the performance and stability of thin-film transistors (TFTs). Here, we study the impact of channel layer thicknesses on the operating characteristics of In₂O₃/ZnO heterojunction TFTs prepared via sputtering. The conduction band offset present at the In₂O₃/ZnO heterointerface affects the device's operating characteristics, as is the thickness of the individual oxide layers. The latter is investigated using a variety of experimental and computational modeling techniques. An average field-effect mobility (μ_FE) of >50 cm² V⁻¹ s⁻¹, accompanied by a low threshold voltage and a high on/off ratio (∼10⁸), is achieved using an optimal channel configuration. The high μ_FE in these TFTs is found to correlate with the presence of a quasi-two-dimensional electron gas at the In₂O₃/ZnO interface. This work provides important insight into the operating principles of heterojunction metal oxide TFTs, which can aid further developments.

Solid-state transistor sensors that can detect biomolecules in real time are highly attractive for emerging bioanalytical applications. However, combining cost-effective manufacturing with high sensitivity, specificity and fast sensing response, remains challenging. Here we develop low-temperature solution-processed In ₂ O ₃ /ZnO heterojunction transistors featuring a geometrically engineered tri-channel architecture for rapid real-time detection of different biomolecules. The sensor combines a high electron mobility channel, attributed to the quasi-two-dimensional electron gas (q2DEG) at the buried In ₂ O ₃ /ZnO heterointerface, in close proximity to a sensing surface featuring tethered analyte receptors. The unusual tri-channel design enables strong coupling between the buried q2DEG and the minute electronic perturbations occurring during receptor-analyte interactions allowing for robust, real-time detection of biomolecules down to attomolar (aM) concentrations. By functionalizing the tri-channel surface with SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) antibody receptors, we demonstrate real-time detection of the SARS-CoV-2 spike S1 protein down to attomolar concentrations in under two minutes.