We report the suppression of oxygen vacancies (O-v) defects in BeO alloyed ZnO films. The alloy films are grown by plasma-assisted MBE on the sapphire substrates with a designed buffer layer. The decreased formation of O-v with the increase of Be content in BeZnO alloys is confirmed by the X-ray photoelectron spectroscopy and positron annihilation spectroscopy measurements. Hall measurements show a "V" curve of the electron concentration and a flip-over "V" curve of the electron mobility as a function of Be content. The turning points of both curves are for the samples prepared at T-Be = 960 degrees C. The turning points imply that there is a narrow growth window for optimum electrical properties of the BeZnO alloys, where the background electron density is almost one order of magnitude lower than the others, while the mobility is four times higher. The results on electrical properties are also supported by high-resolution XRD. (C) 2013 Elsevier B.V. All rights reserved.