Aluminum doping induced columnar growth of homoepitaxial ZnO films by metalorganic chemical vapor deposition

The effect of aluminum doping on the growth of ZnO films on c-plane ZnO (0001) single crystal substrates during metalorganic chemical vapor deposition was investigated. It was found that aluminum doping induces a growth mode of three-dimensional columnar growth. X-ray photoemission spectroscopy demonstrates that partial aluminum is segregated to the growth front. A combined experimental contact angle measurements and theoretical first-principle calculations suggest that the surface energy of the films is promoted by aluminum doping. Besides, aluminum doping also tends to decrease the adatoms diffusion mobility. We conclude that aluminum acts as an antisurfactant element during the homoepitaxial growth, and it increases the difficulty in obtaining high quality n-type ZnO films.