ZnO nanowires are known as promising candidates for thedevelopment of highly efficient mechanical energy transducers usingbiocompatible and noncritical materials. However, the decoupling of thedifferent contributions to the piezoelectric response of ZnO nanowirescoming from the dimensionality effect, the nature and amount of defects,the density of free charge carriers, and the nature and density of surfacetraps is still lacking. The growing attractivity of mechanical energytransducers thus necessitates a thorough study on the interplay among thepiezoelectricity process, free charge carrier screening, and surfacedepletion effects in these semiconducting nanowires as well as theirrelationship to the dimensions of ZnO nanowires. To this day, the growthof ZnO nanowires by pulsed-liquid injection metal−organic chemicalvapor deposition has been less explored despite the excellent structuraland optical properties of ZnO nanowires. By fixing all growth conditionsexcept for the growth time, the impact of the dimensions of ZnO nanowires on their piezoelectric and physical properties is carefullyassessed. Based on electrical characterization and cathodoluminescence measurements, the densities of free electrons and of surfacetraps are determined in the ranges of 1.8 × 10$^{18}$ to 3.3 × 10$^{18}$ cm$^{−3}$ and 5 × 10$^{12}$ to 1 × 10$^{13}$ cm$^{-2}$, respectively, and are shown tovary with the radius of ZnO nanowires. The incorporation of Al$_{Zn}$ and carbon species in ZnO nanowires is further responsible fortheir high electrical conductivity. Furthermore, the piezoelectric response of ZnO nanowires is experimentally determined bypiezoresponse force microscopy and compared with theoretical computations based on finite element method simulations, showingthat the piezoelectric coefficient in the range of 4.5−5.5 pm/V strongly depends on the dimensions of ZnO nanowires as an ultimatetool to enhance the performance of the related mechanical energy transducers.