Single-phase cubic Zn(In)Se thin film growth by Se vapor selenization of Zn(In) alloy precursors films is described. Depositing the Zn(In) precursor film at higher substrate temperatures changes the In/Zn composition and also yields highly crystalline Zn(In)Se films. The In/Zn ratio in the selenized film is higher in comparison to that of the precursor due to differential selenization kinetics and the complex In-Se and Zn-Se reaction chemistry. The resistivity of the Zn(In)Se film depends on the In/Zn ratio. Initially, the resistivity increases with increased indium incorporation due to increased defect concentration and then decreases at higher In/Zn ratios because of lower grain-boundary effects and reduced trap density owing to improvement in film crystallinity. Treatment with vapor-phase Zn compensates for Zn vacancies in the film, reduces electrically inactive defects, and increases doping efficiency, thereby lowering the resistivities to -1 Omega cm. Hot-probe and thermoelectric power measurements show that all low resistive ZnSe films are n-type.