Investigation of the Effect of Doping Concentration on the Electrical Properties of Locally Synthesized Zinc Oxide Semiconductor

Zinc oxide is a wide-bandgap semiconductor material with diverse applications in solar cells, gas sensors, and piezoelectric devices. Controlled doping of zinc oxide with transition metal ions enables precise tuning of its electrical and optical properties for specific applications. This study investigates the effect of varying aluminum doping concentration on the electrical resistivity and carrier concentration of zinc oxide thin films synthesized by chemical bath deposition in the Materials Physics Laboratory of the University of Calabar, Cross River State, South South Nigeria. Aluminum-doped zinc oxide samples were prepared at doping ratios of 0 percent, 0.5 percent, 1 percent, 2 percent, and 4 percent by atomic weight using zinc acetate and aluminum nitrate precursors. Electrical measurements including resistivity, carrier concentration, and Hall mobility were performed using a four-probe van der Pauw measurement system at room temperature. Results indicate a minimum resistivity of 3.6 times 10 to the minus 3 ohm-cm at 2 percent aluminum doping, corresponding to maximum carrier concentration and Hall mobility values. Over-doping at 4 percent aluminum caused a reversal due to defect scattering mechanisms. The study contextualizes findings within the current literature on transparent conductive oxides and discusses implications for fabricating low-cost electrodes for Nigerian dye-sensitized solar cell research programs. Keywords: zinc oxide, doping, electrical resistivity, semiconductor, chemical bath deposition