Significant Carrier Concentration Changes in Native Electrodeposited ZnO

We show that unintentional hydrogen doping of ZnO during the electrodeposition process can impact the material's carrier concentration as significantly as others have reported for intentional extrinsic doping. Mott−Schottky analyses on the natively n-type electrodeposits show a decrease in the carrier concentrations from 1021 to 1018 cm−3 with increasing overpotential. A strong link exists between larger optical band gaps (determined from diffuse reflectance spectroscopy) and higher carrier concentrations, which suggests that hydrogen-based doping underlies the n-type conductivity (Moss−Burstein effect). We propose that kinetic defects introduced during growth at larger overpotentials compete with hydrogen doping, thereby leading to lower net carrier concentrations. This has important implications for using the deposition potential to tune other electrodeposit properties such as the growth rate and morphology.