Effects of thickness and deposition temperature of ALD ZnO thin films on the improvement of electrical properties through dedicated low temperature annealing post-processing

This study investigates how layer thickness and deposition temperature affect the structural and optoelectronic properties of ZnO layers deposited via atomic layer deposition (25–800 nm, 150–200 °$C$). Optical band gaps increased logarithmically with both thickness and temperature, diverging from earlier reports. XRD analysis revealed minimal residual stress but notable changes in texture. Detailed evaluation of optical band gap, refractive index, Urbach energy, crystallite size, and resistivity revealed consistent trends. A specific thickness limit to self-recovery effect and annealing window was identified for optimal property recovery. Unlike previous studies, resistivity was significantly reduced — by up to fivefold — through enhanced mobility and carrier concentration, confirmed by Hall effect and electrochemical profiling. Photoluminescence analysis showed decreased nonradiative recombination and increased Zn interstitials. Importantly, these insights help bridge gaps in understanding annealing behavior and support the design of high-performance ZnO-based devices.