Examination within a Photonic Memory-Based Framework: Al and In Dual-Doped ZnO Thin Film UV Photosensor Devices

The main focus of our study is to examine and report the room-temperature enhancement of the optoelectronic and photoresponsive performance of ZnO materials induced by dual doping with Al and In, achieved by tailoring the materials' structural and morphological characteristics. Structural analyses confirmed the formation of the hexagonal wurtzite ZnO phase, while doping induced noticeable modifications in the microstructure and morphology of the films. The crystallite size was found to decrease from 54.96 nm for undoped ZnO to 38.66 nm for ZnO/1.0% Al/1.0% In films, indicating dopant-induced grain refinement. Also, morphological analysis revealed that the particle thickness decreased from ∼400.1 to ∼201.6 nm, resulting in an increased surface:volume ratio. We conducted a systematic investigation focusing primarily on their persistent photoconductivity characteristics. Further analyses were performed to examine the detailed mechanisms of photocurrent generation, to observe photonic memory effects, to determine photosensor properties and device sensitivity, and to assess the effects of traps. The sensor devices were tested under a UV light source with a wavelength of 400 nm and an intensity of 75 μW/cm², within the range of -5 to 5 V. In a dark environment, the current of the undoped ZnO film was 4.35 × 10^-6 A, while in the 1.0% Al/1.0% In dual-doped device, this value increased approximately 11 times under UV illumination, reaching 2.11 × 10^-4 A and yielding the highest photocurrent. Fast decay component τ₁ showed similarity across all samples, varying between 24.74 and 35.68 s. The slow decay time (τ₂) determining the memory capacity of the devices was measured as 302.89 s for undoped ZnO, while in the 1.0% Al/1.0% In doped sample, this time constant increased to 533.31 s, reaching its highest value. Our findings provide a basis for designing advanced photoactive materials for use in optoelectronic applications. They also indicate the optimal doping ratio for ZnO doped with 1.0% Al and In, supporting its potential use in photonic memory applications, such as multilevel data storage and optical programming.