<p>The detection of atomic and nuclear radiation is becoming increasingly critical due to nuclear threats, accidents, essential environmental monitoring, and recent nuclear disasters. Inorganic and organic semiconducting materials can be utilized in the Schottky diode structure for sensing and detecting gamma rays. In this work, undoped and Ga-doped ZnO (ZO and GZO) nanoparticles (Ga: 2, 4, and 6 wt%) were synthesized using a hydrothermal method at a novel reaction time of 5 h and a reaction temperature of 160 °C. Additionally, the nanocomposites of ZO-PS and ZnO:Ga-PS were prepared via the drop-casting method. Schottky diodes were constructed with the structures Au/ZO-PS/Au and Au/GZO-PS/Au. The structural, morphological, topographical, and photoluminescence characteristics of the prepared samples were investigated based on Ga dopant content. The current–voltage (I-V) characterization of the fabricated Schottky diodes was studied under non-radiative conditions and gamma irradiation for 10, 20, and 30 min. The I-V diode parameters were measured at different irradiation times and varying Ga contents. The results indicated that the diode current increased with longer irradiation times and higher Ga dopant content, while the Schottky barrier height decreased with increasing Ga dopant content. The optimal Schottky diode parameters were observed at a rapid irradiation time of 10 min, where the diode current increased from 1.75 to 13.1 × 10⁻⁷ A, and the Schottky barrier height decreased from 0.71 to 0.66 eV for undoped and 6 wt% Ga-doped ZnO, respectively. Furthermore, the significant increase in diode current (I) values at a low irradiation time of 10 min can serve as a foundation for designing and constructing a sensitive gamma ray sensor and detector. Additionally, the results suggest that Au/ZO-PS/Au and Au/GZO-PS/Au-based diodes can function as gamma ray sensors and detectors.</p>