We study the electrical properties of heavily Al-doped ZnSe grown by molecular beam epitaxy, whose electron concentration is saturated. Hall measurements show that electron mobility decreases with the increase of Al cell temperature, while it is almost independent of measurement temperature. These phenomena can be explained in terms of scattering mechanisms by ionized impurities and point defects. The point defects, which are induced by the incorporation of excess Al atoms, result in carrier compensation in heavily Al-doped ZnSe and decrease the electron mobility. As Al concentration increases, deep level emission around 2.25 eV, associated with a point defect such as a self-activated center [Al-Zn-V-Zn], develops in photoluminescence spectrum. The line width of (0 0 4) X-ray rocking curve is broadened due to degradation of crystal quality, which is induced by the increase of point defects with an increase of Al concentration. As a result, it is suggested that the carrier compensation in highly Al-doped ZnSe is dominated by generation of complex point defects such as self-activated centers [Al-Zn-V-Zn]. (C) 2002 Elsevier Science B.V. All rights reserved.