We have investigated optical properties and electrical properties of electrically degraded ZnSe layers by heavy Al doping, where their electron concentrations lie in the range of 7 X 10(17)-6 X 10(18) cm(-3). Low-temperature photoluminescence exhibits two dominant radiative trap centers of 1.97 eV (RDI) and 2.25 eV (RD2), which are ascribed to V-zn-related complex defects. Deep-level-transient spectroscopy shows two electron-trap centers at 0.16 eV (ND1) and 0.80 eV (ND2) below the conduction-band minimum. On the other hand, it is found that RD2 is dominant in relatively lightly doped ZnSe:Al layers below 7 X 10(18) cm(-3) and RD1 is dominant in more heavily doped layers near 1 X 10(19) cm(-3), while ND1 and ND2 are independent of A1 doping concentration and their trap densities are estimated be below 3 X 10(16) cm(-3). This indicates that RD1 and RD2 cause the carrier compensation in heavily doped ZnSe:Al layers. Their electron transport mechanism can be explained by ionized-impurity scattering mechanism. (C) 2008 American, Vacuum Society.